Ch2_OringerR

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**Ross Oringer Chapter 2 Wikilog**

Chapter 2- Section 1
**Sports Science Video** 11/4/10 http://www.youtube.com/watch?v=hBNo1jj1h54 ESPN is not only the nation's leader in sports news, but it also includes a series of shows calls Sports Science. These shows discuss the physics behind the abilities of certain professional athletes who especially excel in their specific sport. Though there are many, the video with Ndamukong Suh caught my eye the most. Suh was a top pick of the 2009 NFL draft. He is a monster, and is known for his power coming off the line. The video discusses a lot of physics and it is very interesting to know the science behind his actions. Within each episode, the program director has each player run a few tests. The first one is to test his reaction time and acceleration coming off the line. Suh reacts to a trigger in 26 hundreths of a second. He hit a top speed of 13.5 mph in 1.3 seconds. Suh's acceleration and speed reveal that the 300 pounder is faster than quarterbacks. The next test is to navigate through heavy bags and hit the crash test dummy. He hit the dummy with over 3200 pounds of force. This is compared to a freight train! His speed and power makes Suh a dominant defensive lineman in the NFL.

11/8/10 I see kids playing soccer. It shows one person in basically a strobe image about to kick a ball. The bug tries to push the ball, and its not really going anywhere. The mouse hurts its foot. Also, there is a person who is not getting a running start. The ball is a certain distance away, and he is kicking up, but obviously not kicking the ball. The more force behind the kick, the further it will go.
 * What Do You See? **

11/8/10 Momentum: once you obtain a high speed, you can keep this speed. On the ice, there isn't much friction because there isn't a force acting on it. The force of inertia plays a role in this. Figure skaters can glide across the ice with little effort, and a ball rolls across a field after being kicked because of inertia. Once an object is in motion, it will stay in motion. It stops when the force stops.
 * What Do You Think? **

11/8/10 Hypothesis: They should share a similar relation. The ramp makes a parabolic shape, with both sides having very similar, if not the same slopes. The initial height is the valuable measurement to determine the maximum height. 1c. The initial height is 5.32 meters. 1e. The vertical height of the highest point on the opposite side of the track is 5.32 meters. 2a/2b. His maximum height will be about the same simply because the initial heigh is the same. Even though the opposite track is less steep in slope, it will still travel up 5.32 meters because that is the initial height. 3a. It was the same. My prediction was correct because he is going the same speed because the initial height did not change. 3b. The initial height will be the highest point in which you change direction. 4a. It will remain the same (5.32 meters.) 4b. My predictions was correct. 5a. No, because there is no slope to reach a maximum height. 5b. However long until forces make it come to rest. 5c. Momentum would keep the ball on track. 5d. The skater went off the track. 6a. The length is increasing. 6b. It will be equal to the initial height. 6c. The heights are always equal. 6d. The skater (ball) will keep moving until forces act upon it and stops.
 * Investigate **

11/8/10 **Summary**: Galileo Galilei is a physicist, methematician, astronomer, philosopher, father of modern science. He observed that a ball that rolled down one had the same height when it rolled up another ramp. He imagined a ball made of really hard material set into motion on a horizontal, smooth surface. In conclusion, he said that the ball would continue its motion on the horizontal surface with constant speed along a straight line to the horizon. An object remains at rest unless something causes it to move. *Objects will continue to move as they already are. The law of inertia is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. Moving objects may continue to move forever unless a force, push or pull, stopped it. Objects do not stop on their own: they stop because of an unseen frictional force. *Inertia is a property of matter that resists changes in motion (acceleration). It is measured by getting the mass. Weight is subjected to gravity and mass is how much matter an object has. Newton's first law of motion: in the absence of an unbalanced force, an object at rest remains at rest, and an object already in motion remains in motion with constant speed in a straight-line path. Mass is the amount of matter in an object, or tendency to resist a change in motion. The more mass, the greater the inertia. Speed does not affect inertia. Speed is the change in distance per unit of time Velocity is the speed in a given direction. Acceleration is the change in velocity per unit of time. Speed of javelin is the sum of each of the speeds: hand, elbow, shoulder, body. If you run with a ball prior to throwing it, the ball gets your speed before you even try to release it. Therefore, if running at 15 m/s, the ball will get the additional 15 m/s. Frame of reference is a vantage point with respect to which position and motion may be described. Running start: increase distance and or speed to give advantage Frames of Reference: "relative to" a plane in the air, it looks like your not looking. On the ground, you go as fast as the plane is moving. Adding or subtracting to get these relative values.
 * Physics Talk**

1. Inertia, is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. Also, it is the property of matter that resists changes in motion. 2. Newton's first law of motion states that in the absence of an unbalanced force, an object at rest remains at rest, and an object already in motion remains in motion with constant speed in a straight-line path. (An object in motion stays in motion.) 3. Am external force (friction) is needed to act on an object to stop it from moving at a constant speed. 4. A frictional force working that you cannot see that stops the object. 5. Of the two, the one with the greater mass will have the greater inertia. 6. A frame of reference is important because you need a perspective. It is different from the person's point of view in the train or outside of the train. It is the respect to which position and motion may be described.
 * Checking Up **

11/10/10 1a. The ball will roll forever (unless an unbalanced force hits it.) 1b. Newton's first law of motion states that an object already in motion remains in motion with constant speed in a straight-line path. 2. It will reach the same vertical height (20 cm.) 3. I don't think that it would be possible to have an object move in a straight line forever. There are always forces in different places. Not every surface is the same material, and air is not the same pressure and consistency in every location. There is always a different amount of friction which is put into play. 4. The puck glides across the ice. It keeps moving in a straight line until it hits the stick. The stick in this case is the unbalanced force which causes the puck to stop moving. Players will purposely have the puck hit the wall so it will reflect and go into a different straight motion. 5. The person sees it go by at 7 m/s --> (2.5+4.5) 6. The javelin (in perspective of the ground) is 14.5 m/s (10.3+4.2) 7a. (5.6+2.4) 8 m/s forward *relative to the ground 7b. (5.6-2.4) 3.2 m/s forward *relative to the tracks when pushed towards the rear: 7c. *Pythagorean* 6.1 m/s at 67 degrees from cars direction; v = square root of (5.6^2 + 2.4^2) 8. The arrow left the bow at 67 m/s (subtract) 9a. sin45 x d = 15 cm; d=15/sin45= 21.2 cm 9b. sin20 x d = 15 cm; d=15/sin20= 43.9 cm 9c. sin15 x d = 15 cm; d= 58 cm 9d. sin5 x d = 15 cm; d= 172 cm 10a. Newton's First law in 3 sports: Hockey is one example. The puck will stay at rest and will continue to do so unless a force is acted upon it. When it is pushed with force, it will stay in a straight line motion, gliding, until it comes to a rest when hitting a stick. In crochet, the ball will remain at rest if its not forced upon. It will move in a straight motion forever until stopped by another stick or one of the posts in which the ball must go through. In soccer, if the ball if not touched, it will stay still at rest. When kicked, it will go in a straight line constantly until it is stopped by whatever is in play. 10b. Sportscaster (John is the athlete in all sports) Soccer: John passes the ball to his teammate, who then stops the ball. The teammate kicks the ball after taking a running start. The goalie saves the ball, stopping the ball from going into the net. The ball is getting lined up for a goal kick, and it sitting at rest on the field. Crochet: John hits the ball through the posts. It was going straight through successfully. Next round, his ball hits the post, and can not go through. The force acting on it was the post, and unfortunately, he must go again. The ball remains at rest before his next shot. Hockey: John is approaching the puck, while it is sitting there at rest. He hits the puck, and it travels in a straight line, gliding across the ice. He passes it to his teammate, who stops the puck from moving, and has it in control. He hits it off the boards, and changes the direction, until another teammate traps the puck.
 * Physics To Go**

11/10/11 Figure skaters are capable of moving across the ice effortlessly because ice has very little friction. When the push off the ice and gain speed, they can maintain this because they used force to move forward, and there is not much force able to stop the skater from coming to rest. In soccer, when running up to the ball getting ready to kick it, the ball is originally at rest. When kicking it, you apply force to the ball, and it goes forward, rolling across the grass. It continues to roll because it has momentum, and there are no forces strong enough to stop it from rolling, until the friction of the grass eventually causes it to come to rest. The force or the initial height in the case of the ball on the track affect the horizontal speed. Mass also plays a role. The ice skater's speed is determined by the push off/start. The soccer ball's speed is determined by the running start of the player kicking the ball. Due to the meaning of newton's law, they keep moving until or unless they come into contact with an unbalanced force.
 * What Do You Think Now?**

11/10/10 http://dsc.discovery.com/fansites/mythbusters/db/sports/sliding-into-base-faster-than-running.html Sliding vs. Running has been a long debate in baseball forever. The main question is: Which gets you to the base faster? As you run to a base, your body's mass combined with your speed creates momentum. It changes into angular momentum as you go into a slide. The friction created with the ground doesn't slow you down as much as you might think. You lose a little speed, but keeping your body stretched out may enable you to touch base sooner than if you kept running the whole way. If you continue running, your momentum will try to keep powering you forward as you near the base, so you'll slow your speed to stay upright when you stop on base. This adds time to your sprint.
 * Inquiring Further**

**Chapter 2- Section 2**
- Hockey: The puck is moved and travels at a constant speed across the ice - Soccer: The person gets a running start, kicks the ball, and the ball rolls after with constant speed - Crochet: The crochet ball is hit by the stick, and it travels with constant speed
 * Sports with constant speed motion**

11/10/10 I see the guy on top slowly sleep walking. The guy on the bottom is happy, running as fast as he could to his lover because he has a heart in his speech bubble and a bunch of flowers in his hand.
 * What Do You See?**

11/10/10 100 miles per hour is the velocity of some pitcher's pitches in the MLB. This is extremely fast, and its difficult for the batter to react, swing, and hopefully make contact. Picture a car traveling at a top, constant speed of 100 mph. 100 mph relates to velocity, which is speed of direction. The pitch is thrown at this high speed, and its usually a fastball in the area of the batter's reach.
 * What Do You Think?**

11/11/10 **Summary**: Acceleration is a change in the velocity of an object over a certain amount of time. A=deltaV/time. Acceleration is different than velocity, in that it can include change in direction. Its measured in meters per second squared. Speed, or velocity, is the amount of distance covered in reference to time. Average speed is the total distance over the total time. Instantaneous speed is the speed measured during an instant. Average velocity is how fast position changes (large distances and or large times over which there may be variations) Acceleration is how fast speed changes. Positive acceleration-increasing velocity Negative Acceleration-decreasing velocity *The assumption is that velocity is positive. With negative velocity,its the opposite. When V and A have the same signs, it is increasing speed. When the signs are opposite, it is decreasing speeds.
 * Physics Talk**

1a. For constant speed, the distance between the "ticks" are equal distances apart. 1b. Positive acceleration is demonstrated by the following: It gradually increases in speed, so the distance between the ticks grow further apart because its covering more ground in less time. 1c. Negative acceleration is the opposite: by decreasing speed, the distances between the ticks grows closer together over time. 2. Vav = change in d / change in t; Vav = 400m / 50s; Vav = 8 m/s 3. instantaneous speed is the speed at a single instant (spur of the moment occurrence). Average speed takes into account several instantaneous speeds. 4. *CONVERT SECONDS TO HOURS (10 divided by 3600): a = change in v / t;= 100-0/.0028=36,000 km/h squared
 * Checking Up Questions **

11/13/10 1. Average speed is a compiled number of distances traveled over a compiled number of times it took to cover those specific distances, in the form of an average velocity. Instantaneous speed is a single occurrence, meaning that it is the speed at that instant. 2a. Vav=d/t *1km=1000m; 1000m/15s= 66.7m/s 2b. Vav=d/t; 84m/6s= 14m/s 2c. Vav=d/t; 9.6km/2h= 4.8km/hr 2d. Vav=d/t; 400km/4.5hr= 88.9km/hr 3a. negative 3b. positive 3c. not occuring (steady) 3d. negative 3e. not occuring (constant) 3f. not occuring (constant) 4a. constant increase in speed: A, D 4b. constant speed: B 4c. greatest change in speed in each second: A, C 4d. first increased but later decreased: C 4e. A was positive and constant. B had no acceleration. C had increasing than decreasing. D had increasing. 6. *conversion: = 12.5 m/s A= delta v/t; 12.5m/s / 9= -1.4m/s^2 7a. constant speed 7b. increasing speed 7c. slow constant, increasing, faster constant, decreasing, slow constant 7d. decreasing, constant, increasing 8. Vav=d/t; 100mi/2h= 50mi/h 9. If the person's average speed was 15m/s, this doesn't mean the instantaneous speed is the same. Average speed is calculated from a compiled list of trials, in the form of an average. The instaneous speed could have been 15m/s at one point, if lucky 10. x..x...x.....x......x.......x...........x...........x (very close in the beginning shows at rest and then further distance apart shows constant increasing speed) 11. a= delta v/t; 4= delta v/5; delta v= 20 m/s 14a. kicking a soccer ball 14b. sprint 14c. golf ball slowing down as it reaches the hole 14d. track race 14e. backstroke swimming
 * PTG**
 * 45km || 1000m || 1 hr ||
 * || 1km || 3600 s ||

11/16/10 REBOUNDING: bouncing off a surface and changing direction *assume acceleration is constant throughout the entire process 3 stages of process: fall down to ground, compresses until stopping, and bounces back up 1. a=vf-vi/t; a=.5-(-.5)/1=1m/s2 a=.5-(-.5)/.1=10m/s2 a=.5-(-.5)/.01=100m/s2 *The harder the surface, the less time it takes you can have small velocities, but the less time, the greater the acceleration 2. a=vf-vi/t; .5-(-.5)/.2= 5m/s2 3a. 5m/s2. It is going downward at this acceleration. 3b. 5m/s2. 3c. 5m/s2. They are all the same for the three stages. *In a v-t graph, the slope (acceleration) is a straight line because it is constant. The slope is 5m/s2.
 * Physics Plus (page 152)**
 * __** velocity **__ || __** acceleration **__ || __** examples **__ ||
 * small || small || golf cart ||
 * small || big || rebound ||
 * big || small || big truck ||
 * big || big || airplane ||

11/15/10 In terms of velocity, the numbers are represented with the label of km/h, mi/h, or meters per second. These represent velocity because the number is the amount of ground covered in an elapsed period of time. Therefore, if you travel at a speed of 45 meters per second, your velocity literally means that you cover 45 meters per one second. You figure out the answer from gaining information of distance and time, over however much time/distance is required. 100 mi/h is the same idea with different label. It just means that the object moves at 100 miles in one hour.
 * What Do You Think Now?**

11/15/10 All these terms related to velocity can be seen in numerous sportscasts. One sport where we see much of this would be NASCAR. Constant speed is basically the cruise control the car reaches: a constant high, average speed that the car travels over a certain period of time. In the beginning, the car is at rest. Over time, the car accelerates to its highest speed, and eventually reaches constant velocity. God forbid there was a crash, or when the car needs a pit stop, the automobile will ride the brakes, decreasing speed to an eventual stop.
 * Reflecting on the Section and the Challenge**

Chapter 2- Section 3
11/16/10 The person (first) is moving at a very slow pace, and the ball is not going very fast. The person (second) is moving at a faster pace, and ball is moving faster. The person (third) is sprinting, and the ball is moving at the fastest speed. The dog on the image corresponding to the person below represents this as well. The dog walking represents the slowest speed. The dog sprinting represents the middle speed. The dog in the car is moving at the fastest speed.
 * What Do You See?**

11/16/10 Force is the push/pull behind an object. In the case of tennis, the force is seen in the serve and the forehand/backhand. In a serve, the ball is thrown in the air, the player shifts all their weight towards the ball, and hits the ball as hard as possible. This force makes the ball move at fast speeds. Plus, it can move at 100 plus miles per hour because the mass of the tennis ball is small. If you were to serve a bowling ball, you wouldn't be able to hit it as fast at all. This is because the bowling ball has a much greater mass. The less mass, the more force able to move the object faster and further. The opposite goes for an object with more mass.
 * What Do You Think?**

11/16/10 **Summary** (pages 160-165): The difference between qualitative and quantitative is simple. Qualitative (quality) is the descriptive observations, for example sticky, smelly, and color. Quantitative (quantity) is a specific number observed. Newton's second law of motion equation is acceleration equals force over mass (a=f/m). A newton is the force required to make one kilogram of mass accelerate at least 1 m/s2. Newton's second law tells you that accelerations are caused by unbalanced forces. The larger the mass, the more force required for a higher acceleration. Significant figures: when adding and subtracting, the final answer should have the same amount of significant figures as the measurement with the fewest significant figures. For multiplication and division, the result should have no more than the factor with the fewest significant digits.
 * Physics Talk (160-165)**

1. Newton's second law of motion explains how an object will change velocity if it is pushed or pulled upon. Acceleration equals force over mass. Acceleration is directly proportional to the force. Acceleration is indirectly proportional to the mass. 2. Acceleration is indirectly related to mass. If force were constant, and mass were to be increased, than acceleration would decrease. It is simple because if you were to throw a bowling ball, because it has such a large mass, it will have a slower acceleration.
 * Checking Up Questions **

11/17/10 **Summary**: Newton's second law states that if there is an acceleration, there must be an unbalanced force acting. Gravity is the force that bent the ruler in the investigation. Force of gravity is weight. Weight depends on the mass of the object and the acceleration due to gravity. w=mg. W is force, m is mass, and g is acceleration due to gravity. The constant acceleration on earth is 9.8m/s2. When a force acts on an object, it accelerates. If two forces are in opposite directions, than the net force can end up being zero. A free body diagram is a diagram used to show the relative size and direction of all forces acting on an object. Mass is independent of location. Weight is dependent on location. 3. 30 N relates to weight. Weight is the downward force applied to a mass, which is therefore known as gravity. 4. On a planet with higher acceleration, your weight would increase but your mass would remain the same.
 * Physics Talk (166-167)**
 * Checking Up Questions **

11/19/10 1a. 350N (70kg x 5m/s2) 1b. 80kg (800N / 10m/s2) 1c. 10 m/s2 (70N / 7kg) 1d. 80 kg (400 N / 5m/s2) 1e. -15m/s2 (-1500N / 100kg) 1f. -3,000N (100kg x -30m/s2) 3. F=ma: 42N= (.30kg)(a); a=140m/s2 4. F=ma: F= (.040kg)(20.0m/s2); F=.8N 5a. Newton's First Law of Motion: The main reason for this is mass. Mass is a measure of inertia. A bowling ball obviously has more mass than a baseball. The more mass, the more inertia it has. This means, it would require more force to throw a bowling ball further than a baseball. The baseball has less inertia. It is easier to use the force from our bodies to throw a baseball further, therefore, it will accelerate more easily. The bowling ball has larger inertia because it is more difficult to change its motion. 5b. Newton's Second Law of Motion: The equation that describes this is force equals mass times acceleration. A baseball, which has less mass, will have greater acceleration. A bowling ball, with more mass, will have less acceleration. Mass and acceleration are indirectly related. The faster it is going, the more it will hurt the hand. 9. When you throw a baseball, the force of your hand from the initial throw acts upon the ball, until an unbalanced force acts upon it, which would be the person who is going to catch the ball. 10. 50N + 40N= 90 N 11. 200N times 4 people: combined force is 800 newtons. 12. F=am; 125N=(.7kg)(a); a=179m/s2 13. a^2+b^2=c^2; 50^2+120^2=c^2; c=130 at 67 degrees NE 14. a^2+b^2=c^2; 4000^2 + 5000^2= c^2; c=6403N at 53 degrees 15. F=am; F=(12.8kg)(9.8m/s2); F=125N 16a. a^2+b^2=c^2; 30^2 + 40^2; c=50 N at 53 degrees 16b. A=f/m; A=50N/5.6kg; A= 8.9 m/s^2 17a. a^2+b^2=c^2; 30^2 +20^2=c^2; c=36N at 34 degrees 17b. A=f/m; A=34N/100kg=.36m/s^2 17c. A=f/m; A=50N/100kg=.5m/s^2 18. Preparing for the chapter challenge: In baseball, the pitcher throws the baseball with a velocity of 100 miles per hour. The batter, with quick reaction time, hits the ball. The ball has a mass of .145 kg. The batter lines up for the pitch, keeps the weight back, and lunges forward, with all weight behind the hit. He hits the ball with 265N of force, and into the outfield. The outfielder, accelerates, and changes the direction of his motion to track down the ball after it is hit.
 * PTG**

11/22/10 1. 125N north, 125N west: a^2+b^2=c^2; 125^2+125^2=C^2; C=176.8N 2a. Player A (40N north) Player B (70N south); 70N-40N= 30N due south 2b. resultant force on all three players: 70N south-40N north: 30N due south; a^2+b^2=c^2; 30^2 + 40^2=C^2; 2500=c^2; c=50N SW 2c. Southwest
 * Physics Plus**

11/19/10 A force is a push or pull on an object. It is measured in newtons, and acceleration and mass are required to figure out the push or pull applied to an object. A tennis ball and bowling ball are required different forces to move them. Due to mass, a different force is required for both. For a tennis ball, less force is required to move it. For a bowling ball, you need more force to move it because of its greater mass. If the same amount of force is applied to both, the tennis ball would go further because it has less mass.
 * What Do You Think Now?**

Chapter 2- Section 4
I see a girl dropping a red apple straight to the ground,and the numerous apples is basically a strobe photo. It is moving straight down vertically, with different distances apart because motion is increasing. The green apple is being thrown outward, and its motion is represented as going outward, and it looks pretty constant.
 * What Do You See?**

The force behind the object and the force it can encounter while in the air. Wind plays a role, as well with how much power you put into it. Also, mass has an influence. Gravity always has an influence, as well as the angle it was thrown at.
 * What Do You Think?**

1a. They should be about the same, no matter how high you hold them. 2a. They hit the floor at the same time. 3a. No, they still hit at the same time. Distance changed, but the time to fall was the same still. 3b. Yes, the one that went faster horizontally, the further it travelled. 3c. 4a. If it is done at a lower height, they still hit at the same time, it just takes less time to get there. 5a. It will follow with the thrower throughout the whole time the person is being pushed. In the animation, it is thrown up, and landed right back in the bed of the truck. 6a. The vertical component of velocity decreases on the way up. On the way back down, the vertical components get larger and larger. The horizontal components are unchanging. 6b. Range is the distance from where you start until you hit the ground again. Speed affects the range of the ball. Part C:
 * Investigate**

Physics Talk 11/23/10 **Summary**: Projectile motions are commonly seen throughout sports. The horizontal thrown coin and the coin that is just dropped fall at the same time. The horizontal motion doesn't affect the downward motion. Intuition tells you that the dropped coin should drop first. Believing is seeing. The x component and y component of all vectors are independent. Vertical velocity affects vertical motion and same with horizontals. Y is vertical. Acceleration due to gravity is -9.8m/s2. Vertical velocity changes by -10m/s every second when going back downward. Projectile: the only force is weight. They are launched through the air. Ignore air resistance. Trajectory: path of projectile. They are always parabolic in shape. Ground to Ground: two horizontal launches and they are symmetrical around the highest point. At the highest point, the y-velocity is 0. It is continuously moving horizontally. The x and y information are independent from each other. Acceleration on the y axis is always 9.8 due to gravity, and it always points down, making it negative. Acceleration on the x, because the motion is constant, is 0. If this isn't true, it is not a projectile. On a freefall, the only force is weight but its 1 dimensional motion (only vertical.) The vertical positions of a free fall and projectile are the same.

1. If a pen and ruler were dropped at the same time from the same height, they will hit the ground at the same time because there is no air resistance, and acceleration due to gravity acts upon them in the same way. 2. When an object falls vertically down, it won't remain the same because the vertical velocity is constantly changing. 3. If a ball is thrown up in the air, highest point velocity is 0. The acceleration is -9.8m/s2.
 * Checking Up Questions **

11/28/10 1 and 2. SEE IMAGE BELOW
 * PTG**

4. They all thought that a bullet that is dropped would land faster than one that was shot horizontally. They thought that the velocity, moving horizontally, will remain in the air for a longer period of time. In reality, they will hit the ground at the same time. This is because the vertical velocity is the same, even though the horizontal velocity isn't. 6. A projectile's horizontal motion has no effect on its vertical motion, and a projectiles vertical motion has no impact on its horizontal motion. Vertical velocity changes by -10 m/s every second. Horizontal velocity NEVER CHANGES. Diagrams greatly display this by the stair case view. 7. Neglecting air friction, the arrow that is being dropped and the other arrow being shot horizontally at 50m/s will land at the same time, due to gravity. 8. c=3.6 at 33.7 degrees 9a. 11.98m/s 9b. 23.96 m 10a. 8.5m/s 10b. 4.25m SEE ALL WORK BELOW!!!!! 11. The pitcher winds up for the pitch, and releases the ball with a velocity of 100 miles per hour. The batter, waiting in the batter's box, line's up to swing the bat and make contact with the baseball. He hits the .145 kg ball with 265N of force, and into the outfield. The outfielder, accelerates, and changes the direction of his motion to track down the ball after it is hit. The ball hit high into the air accelerates vertically at 9.8m/s^2. After reaching it's highest point, when velocity is 0m/s, the ball falls down, at an acceleration of -9.8m/s^2, falling into the glove of the fielder.

11/28/10 *The Physics Behind Chipping a Golf Ball* 1 & 2. Trajectory is controlled by club selection. If you want it to go higher, you use a more lofted club. The chip shot is a low running shot, and can be controlled based on we arrange our body over the ball. The loft has an angle. You want to maintain the same loft by keeping hands steady, weight forward. By making the ball go higher, you tilt the club back, and it goes a little higher. The highest trajectory shot is ball forward, hands more towards the middle, the ball goes higher, and it rolls less because of the trajectory. Overall, if you want a low chip shot, you need to lean more over the ball. If you want it to be higher, you need to lower your hands more in order to get more under the ball. The shape of the club to begin with is constant. In order to change the trajectory, one can personally change the position of the body and hands.
 * Video Clip**
 * http://www.youtube.com/watch?v=9rsbaoxjs6k **

11/30/10
 * Physics Plus**

11/28/10 In order to determine how far an object will move while in the air, you need to measure/determine launch velocity and initial height. When your launch velocity is increase/decreased, and when your initial height is increased/decreased. As the initial height increases, the range increases as well. The relationship (increase or decrease) between launch velocity and initial height is valuable information.
 * What Do You Think Now?**

Chapter 2- Section 5
I see a girl kicking it behind her high in the air. When it comes down, it lands on another person's head, and bounces off. The original kick had a high vertical projectile (parabolic shape), and the projectile for the kid when it hit off of his and went into the net was not as tall.
 * What Do You See?**

Angles greatly affect the projectiles when launched from the ground. The larger the angle, the further tilt back it is, and the higher it will go in the air. Like in soccer, when you lean back on the ball when kicking it, it goes over the net. When decreasing the angle, it doesn't go as high in the air. Launch speed greatly affects the range, even when the angle is constant. If there is more force applied, the object will go further. In terms of soccer, if two kids kicked a ball at the same angle, and one kicked it much harder than the other, it would obviously go further (range).
 * What Do You Think?**

12/1/10 **Summary**: Projectile has two motions that act at the same time, having no affect on one another. One of them is constant along a straight line, and its affected by launch speed and direction. The other is downward acceleration, which is a constant of -9.8m/s^2. This is affected by launch. The math model has a table of times, distances, and speeds during the fall. The physical model is the even spaced strings of calculated lengths. All projectiles are parabolas (omitting air resistance.) A 45 degree launch produces the greatest range, or the largest distance covered. Small angles have greater horizontal velocities, but less hang time. Larger angles have greater hang time and less horizontal velocity.
 * Physics Talk**

1. The two types of motion are constant and downward acceleration. 2. For a model to be accepted, it must match reality in nature. 3. Height and range with different angles; 45 degree launch produces the greatest range. When pairs of angles add up to 90 degrees, distances will become identical. When going from 10 to 80, horizontal velocity increases and vertical decreases.
 * Checking Up **

12/2/10
 * Page 192 Problems**

12/3/10 1. If launching and landing heights for a projectile are equal, a 45 degree angle produces the greatest range because that it will cover the most ground. 2a. The greater the angle (over 45), the less distance it will travel because it has a larger hang time, and has a greater vertical component of velocity. 2b. As the angle increases before reaching 45 degrees (up to 44), the greater the range. 3a. 90 degrees - 30 degrees: 60 degrees produces the same range as a 30 degree angle 3b. 90-15= 75 degrees produces the same range as a 15 degree angle. 4. The reason is that people can run faster than they can jump. With a big x component and a small y component, you get a small angle (much less than 45). As y component gets bigger, the angle gets bigger. 5. The reason he was successful is both events was because he got an efficient and good running start in the beginning. Also, he jumped at the best angle which would produce his maximum (vertex of parabola). 6a. a=-g=-9.8m/s^2 DOWN 6b. Vmax=Vix only because Vy is at 0 at the max height 7a. Vertical speed final: 29.4 m/s 7b. horizontal speed after 1 second: 5m/s 7c. 15m from the cliff 8. 45 degrees creates the longest range 9. The angle closest to 90 degrees creates produces the greatest projectile height 10a. direction of acceleration: east 10b. d=vit+.5at^2; -100=-4.9t^2; t=4.5 seconds 10c. 90m from the cliff d=vit+.5at^2; d=20(4.5) + .5(0)(4.5)^2
 * PTG**

12/3/10 45 degree angles produce the greatest range. Complementary angles create the same range. Angles bigger than 45 degrees create a shorter range. Angles less than 45 degrees create a larger range. A more rapid launch speed of a projectile can effect the range (when the launch angle is the same.)
 * What Do You Think Now?**

12/6/10
 * Mini Challenge Videos**

http://www.youtube.com/watch?v=oph9BP4lKjs&feature=related http://www.youtube.com/watch?v=BRAFjy8Hmec&feature=channel

Chapter 2- Section 6
12/10/10 In this image, I see a person getting ready push himself off a wall while sitting in a chair with wheels (left part.) You can tell because his knees are bent, ready to take off. When he takes off, he pushes off the wall, keeps his legs straight in the air, and moves away from it.
 * What Do You See?**

12/10/10 Put the force at the bottom of your body, strain your knees, and bounce up into the air, releasing all force. Force pushed on the floor pushes back on the person. Every force has an equal and opposite force. The force is transferred.
 * What Do You Think? **

12/13/10 **Summary**: Newton's third law of motion states for every applied force, there is an equal and opposite force. The two forces always act on different objects. For example, if you press your finger against the table, the table presses against your finger with the same force. A force diagram shows the forces acting on an object. In a free-body diagram, each force is represented by an arrow. The forces are labeled. Forces always act on different objects. Newton's third law of motion can be described in three equivalent ways: For every force applied to object A by another object B, there is an equal and opposite force applied to object B by object A. if you push or pull on something, that something pushes or pulls back on you with an equal amount of force in the opposite direction. Forces always come in pairs.
 * Physics Talk**

1. Newton's third law of motion states for every applied force, there is an equal and opposite force. Also, forces always come in pairs. 2. The mass pulls up on the force with an equal force of gravity. 3. A free body diagram illustrates the forces acting on an object. Arrows represent the type of force and the direction of this force.
 * Checking Up Questions **

12/14/10 1. Yes, because every action has an equal BUT opposite reaction. 2. No. Restoring forces balance downward weight. Restoring force is equal to the force your putting down. If the material is too weak, than it will break. If the material can't withstand the force, it will break. 3. The bathroom scale is a spring with a needle attached, and then calibrated. It measures weight and force through the equation of mass times gravity. It measures the mass of the body exerting a force on the scale and multiplies it by 9.8. 4. The forces on each other are the same. Break because the fastball is too big for the material to withstand. 5. When a linebacker hits a small running back they may not be exerting the same force on each other. But, since the mass of the running back is smaller, and the acceleration of the bigger player is slower, the smaller guy will move into the direction that the larger guy was moving. 6. The force of the boards on the player is equal to negative the force a player has on the boards. 7. Baseball players prefer to wear gloves when catching a ball because all forces come in pairs so when the ball hits the players glove, his hand is going to need to exert the same force on the ball in order for it to stay in the glove. The glove has some padding which causes lower acceleration which reduces force on hand. 8a. John is skating up the side of the rink, and he is immediately slammed into the boards. At initial impact, he exerted a large force on the boards with great acceleration. The boards exerted the same force. Although, due to the larger mass of the boards, they may shake a little, but the player gets shaken as well. Due to no friction, the player could lose footing and fall. 8b. A deflection of the ground can produce a force, if you fell. If you fell, you would be pulling up the force from the ground while pushing down the force of your own. This can be made funny and comical if a major wipeout were to be shown with comical commentary.
 * PTG**

For every action, there is an equal but opposite reaction. All forces come in pairs, in which each acts on a different system. They must be equal in size but point in opposite directions. No matter mass, the forces are equal, but damage will go to the lighter mass object. Forces are equal, but accelerations equal. Smaller mass has a bigger acceleration.
 * Newton's Third Law Class Notes**

12/15/10 When jumping in the air, you are applying a gravitational force downward and a normal force goes through the body upward towards the sky and off the ground. We push down on the floor with force to go up. Newton's third law explains that every force and an equal but opposite force, so therefore, the floor shares this relationship with the person jumping.
 * What Do You Think Now?**

Chapter 2- Section 7
12/15/10 In the first image, the spring scale is attached to the shoe on ice. As seen, due to no friction on ice, the shoe glides with the person while moving. The spring scale shows the person is putting little force in pulling the shoe. The next image, the person attached a spring scale to the boot again, but on sand. Based on the sweat down his face, he is putting much force into the pull, and can't get it to move very fast.
 * What Do You See?**

12/15/10 Some sports require special shoes for slippery grounds, in order to either glide (ice skating) or the gain traction in the ground to ensure there is no falling. A clean, sharp blade of an ice skate should glide on ice. Cleats with spikes at the bottom will allow the person to keep their ground and accelerate in different directions more easily.
 * What Do You Think?**

12/15/10 **Summary**: Force due to friction in this case was between the shoe and the surface. The pulling force applied was equal to the frictional force. The forces were in opposite directions, creating a net force of zero. Normal force is the force acting perpendicularly or at right angles to a surface. Coefficient of a sliding force is a dimensionless quantity symbolized by mu. Mu=force of friction/normal force. The force of friction is equal to the force required to slide the object at constant speed across a surface.
 * Physics Talk**

1. The force of friction is equal to the force read on a spring scale because the force of pulling that was applied to move the shoe was equal to the frictional force. They were in opposite directions, making the net force equal to zero. 2. The coefficient of friction has no units because its a force (newtons) divide by another force (newtons) 3. The force of friction is equal to the force required to slide the object (constant speed)
 * Checking Up Questions **

12/16/10 µ: is the coefficient of friction (has no units); ratio of friction force to normal force; measure of how much two surfaces interact when sliding; almost always between 0 and 1. It is a bigger value when the surface is rough, unless its independent of weight. Its only valid for a particular pair of surfaces.
 * µ Class Notes**

12/20/10 1. Running, an outdoor sport, can be a dangerous sport depending on weather conditions and the running shoes one wears. It is very important to have correct shoes to prevent injury. If running on a wet surface due to rain, the person may want to wear shoes with little spikes that can gain traction on the track, in order to prevent a bad slip. Running shoes are very light, and if the shoe were to be a little heavier, it may be more safe because the shoe can have thicker treads. 2. Ice skating is a sport which requires minimal friction. The skater wants to have clean, sharp blades every time when entering the ice. If the blade is chipped and not well groomed, the skater may fall, and not glide smoothly on the ice. To reduce this friction, skaters clean their skates before and after going onto the ice. 3. This is not true. Every surface is different, no matter what. Her court at home can have more friction than the other court, and therefore, she would need to know certain things to make that assumption. She will need to know the material of the court and how it can react with the sneakers when moving on the court. 4. Tennis players have different sneakers for every different court. On a hard court, you need more friction on the sneaker. For clay, which slows down the game, you don't need as much friction because the clay is rough. For grass, you do not need as much friction. 5. The minimal horizontal force would be 18 newtons. µ=f/N (.03=__/600)=18
 * PTG**

6a. w=mg w= (1000)(9.8) 6b. µ=f/N .55=f/9,800 6c. Fx=MAx f=ma -5390=1000a 6d. Vf=Vi+at 0=Vi+(-5.39)(6) 6e. The original speed was 32.34 m/s. The claim was wrong because he was going faster than he said (29m/s). He had to stop short because he was going faster, causing his stop to be more dangerous and sudden. His decreasing acceleration was -5.39 and it took 6 seconds for him to come to rest.
 * w= 9,800N **
 * f=5,390 N **
 * a=-5.39m/s^2 **
 * Vi= 32.34 m/s; change in speed **

7. Air and water have affects on motion similar to sliding friction. Air resistance and water resistance depend on speed. Most importantly, it is the speed that is changing. For example, when going against the wind, the same wind resistance is hitting my face. 8. If there is a maximum force, it will set a limit on how fast you can start. Even if you have incredibly strong legs and proper shoes, you won't have more acceleration. To solve this problem, friction must be reduced by buying shoes that have a smoother soles on the bottom. 10. Without friction, one can not walk. Friction is important to running because you need to have traction in the ground to for safety so one will not slip and keep their footing. In baseball, football, and soccer, cleats are used because you need friction and spikes to keep footing in different surfaces that may not give you with flat-bottomed sneakers. 11. With 2 minutes left in the soccer match, John is dribbling up the field, hoping to score a goal. He is wearing his indoor sneakers on the wet soccer field outdoors. He is headed towards the goal, makes a sharp left turn, and falls down, giving up the ball. This is pivotal. The reason he lost his footing was because he had no traction between his flat bottomed sneakers and the wet ground.

12/20/10
 * Physics Plus**

12/22/10
 * Lab: Bowling With Blocks**

Part I: Measuring µ 1. 12N 2. 4N 3. 4N, 4N (repeated tension two more times) 4. 5. 6.

// Part II: Chucking the Block // (g) || Mass (kg) || Measured Time (s) || Measured Distance (m) || Ff (N) || Acceleration (m/s^2) || Calculated Vi (m/s) || Calculated Time (s) || % error ||
 * Mass
 * 187.04 || .18704 || 1.64 || 5.3 || .60N || -3.2 m/s^2 || 5.82 m/s || 1.82 s || 9.8% ||
 * 187.04 || .18704 || 1.28 || 3.4 || .60N || -3.2 m/s^2 || 4.66 m/s || 1.46 s || 12% ||
 * 187.04 || .18704 || 1.42 || 4.3 || .60N || -3.2 m/s^2 || 5.25 m/s || 1.64 s || 13% ||

14.

15.

17.

// Part III: Questions/Conclusions // 1. The coefficient of friction in Part I signifies the friction forces interacting between the floor and the block. 2. My calculation of µ was .33. The class calculation was .332. My results shouldn't be the same as everyone else because everyone reads the spring scale differently. Although, they are very close. Random and systematic errors play a role. 3. My percent error was around 10%, which is solid. The percent was relatively low, and my times matched up pretty well. 4. The theoretical physics we are doing applies to the real world, especially through sports. They all display Newton's laws. In order to get the coefficient friction, you need to get two different forces interaction, and this is common and applicable to the real world. 5. Different floors were used (meaning there are different frictions), hand/eye coordination of the person timing, not being able to start and stop at the exact time, and the block to the tape isn't fully lined up correctly.

12/23/10 The force of friction is equal to the force required to slide with constant speed (sometimes tension). Different sports require different, but special shoes because of certain weather conditions and field conditions. Indoor sports like basketball need shoes with good traction so they can keep footing. Also, for tennis, you need proper sneakers to keep footing on the hard surface. But, if you are playing on a slippery and muddy grass field, you would want to wear cleats with spikes to gain traction and a good grasp of the ground. This cleat is smooth and lighter so it can accelerate better in worse conditions, so there wouldn't be a large mu.
 * What Do You Think Now?**

Chapter 2- Section 8
There is some horizontal speed to accelerate and are trying to transform into a vertical acceleration. The pole bends, and there is some flexible force that will help them pole vault to the top of the roof.
 * What Do You See?**

The pole vaulter can't clear a 12 meter fence with a 11 meter pole because it would be heavier, and acceleration would decrease because the object is heavier. Factors that affect this (limit height) are the length and mass of the pole, the deflection (force), and momentum (acceleration).
 * What Do You Think?**

1/3/11
 * Investigate Section 8**

a. We will hold it on the opposite side of the ruler, and there is a line on the ruler that stops the penny. We will hold the ruler pretty far off the ledge. We don't want it to be that flexible. b. The bend of the ruler (deflection) which represents the force you use, elasticity of the material, length of the ruler, placement of the object on the ruler, mass of the object

Experiment: Deflection of the Ruler 1a. The more force used to bend the ruler, the higher the object will go. 1b. We are recording the bend of the ruler by gaining a measurement with another ruler (distance in between). 1c. Tools being used are one ruler for launching, a penny, and another rule to measure the length of the bend. 1d. We will make a chart of the deflection distance and how high it goes, using 5 different trials Conclusion: The greater distance of deflection, the greater the resulting height. Direct Relationship. NOTE: measurements are not exact because we "eye-balled" the resulting height and the deflection cm are not perfect as well due to systematic and random error.
 * Deflection (cm) || Resulting Height (cm) ||
 * 1 || 48 ||
 * 2 || 71 ||
 * 3 || 87 ||
 * 4 || 113 ||

1/3/11 **Summary**: When a force acts on an object, the speed and position may change. Kinetic energy is associated with motion and gravitational potential energy is associated with position. When forces act on objects, energy changes from one form to another. The sum of the kinetic and potential energy remain constant. This concept is known as the law of conservation energy. Work equals force times distance (w=fd). Elastic potential energy was displayed in the ruler investigation. It is the energy possessed by a spring when stretched or compressed. SEE TABLE for all descriptions. Work: W=fd (f is force in newtons, d is distance in meters) Elastic Potential Energy: EPE=1/2kx^2 (k is spring constant in newtons per meter, x is stretching amount in meters) Gravitational Potential Energy: GPE=mgh (m is mass in kg, g is acceleration due to gravity, h is the height in meters) Kinetic Energy: KE=1/2mv^2 (m is mass in kg, v is the velocity in m/s)
 * Physics Talk**

1. A force is required in order for the energy of an object to change. 2. In the investigation, the penny gains its energy from the force that is put on the ruler, then pushing against the penny. 3. The vaulter's kinetic energy is the start of the process with initial speed. All kinetic energy that is left over then becomes elastic potential energy (EPE) so the vaulter can put the pole on the ground, then bend the pole and attempt to reach a certain height. 4. Joules is the units for all energy. The following are required: Work: newtons (N) and meters (m); Gravitational Potential Energy: kg, m/s^2, meters; Kinetic Energy: kg, m/s; Elastic Potential Energy: N/m, m
 * Checking Up Questions **

The Law of Conservation of Energy: Total Energy remains constant but the types of energy can change.
 * Type of Energy || Description || Equation ||
 * Kinetic || Energy possessed by an object when it is moving || KE=1/2mv^2 ||
 * Gravitational Potential Energy || Energy posses by an object when it is above the lowest point || GPE=mgh ||
 * Elastic Potential Energy || energy of a spring due to compression || EPE=1/2kx^2 ||
 * Work || Caused by a force acting over some distance parallel to the direction of motion || W=f*d ||

1/4/11 1. Work is required initially, and then it changes to kinetic, and then changes to GPE, which then changes to kinetic and ends with work out. 2. Elastic potential energy to kinetic energy while swinging, and then there is work on the ball. After work on the ball, that changes to Kinetic, which changes to gravitational, and ends with work out. 3. KEi=GPEf 1/2mv^2=mgh 1/2(m)(12)^2=m(9.8)(h) 72=9.8h h=7.3 m 4. The limiting factor is the initial velocity, plus the work on the pole. The pushing off the pole is minor compared to initial speed. 5. If the temperature increases, it decreases the height because some of the total energy is lost this way (when heat leaves the system).
 * PTG**

6. KEi=GPEf 1/2(m)(v^2)=m(9.8)(4.55) 1/2v^2=44.59 v=9.5 m/s

7. In general, if he went higher, his Vi had to increase. Kei=GPEf 1/2(v^2)=(9.8)(6.14) 10.97m/s

8a. GPEi=KEf (2)(9.8)(100)=1/2(2)(v^2) 1960=v^2 v=44.27 m/s 8b. You can do this calculation without the mass information because mass is on both sides of the equation, and therefore, it would just cancel each other out. When friction is not considered, then you wouldn't have to include work energy.

9a. W=EPEf W=1/2kx^2 W=1/2(1500)(.25)^2 W=46.88J 9b. EPEi=KEf 46.88=1/2mv^2 46.88=1/2(.1)(v)^2 v=30.6m/s

10a. EPE=Wout 1/2kx^2=F*d 1/2(315)(.3)^2=W W=14.2J 10b. W=F*d 14.2=F(.3) F=47.3 N

11. GPE=EPE mgh=1/2kx^2 (.04)(9.8)(1)=1/2(18)(x)^2 x=.21m

12a. Force=mass x acceleration: N=kg x m/s^2 12b. GPE=mgh; (kg)(m/s^2)(m) N*m= J 12c. KE=1/2mv^2 ; 1/2(kg)(m/s)^2 ; 1kg x 1 m/s^2 = J; kgm/s^2*m=N*m 12d. EPE = 1/2kx^2 ; 1/2(Nm)(m)^2; N*m 13. EPE leads into KE which then leads into GPE and finally KE and the water does work to stop him. 14. To get the ball into the air, work is required. The work is turned into kinetic energy, and then to gravitational energy because it goes into the air. 15. The ball, initially at rest, is required work to get moving. The work is transformed into kinetic energy, gaining speed while in the air. The kinetic energy is transformed into gravitational energy, then back to kinetic. Finally, work is done (the ground) to bring it to rest. 16. We are doing baseball, and the question above just about sums it up. A pitcher winds up with a velocity of 85 miles per hour. The batter, getting ready, uses work to swing the bat and make contact with the ball. Gaining speed in the air, the work has transformed into kinetic energy. The outfielder, on his horse, tries to grab the ball while accelerating to get it while the ball is transfered from kinetic to gravitational potential energy. The ball goes out of the park,and work brings the ball to rest.

1/5/11 Speed is the valuable component to this situation. A person's height can not just increase that shortly. If speed is increased, distance will as well. Also, the pole is not able to just increase in size because it has to be a standard height. The higher initial velocity, the more kinetic energy involved, which then transfers to a high elastic potential energy, which will then lead to the gravitational potential energy, making the competitor gain a good height.
 * What Do You Think Now?**

Chapter 2- Section 9
Figure skater has jumped in the air, spinning, and the helicopter is timing the hang time.
 * What Do You See?**

No, it isn't possible for some athletes to defy the pull of gravity. It is a set pull, and will not change for certain people. No matter who it is, gravity is the same, even if one athlete is better than the other. A world class figure skater does not defy gravity to remain in the air long enough. They are skilled to get a good initial velocity to spring into the air for as long as possible.
 * What Do You Think?**

1/6/11
 * Investigation Section 9**

**Prelab**: *Hang time doesn't exist. They were in the air, but they came down due to gravity.

1. Work begins when the person bends down, then when the unbend and push up, the jump begins, and gravitational potential energy begins. 2a. We will find out how much force and energy are needed to complete a vertical jump. 2b. We will initally take the height from the hip and get the change in distance when bending down to begin the jump. We will also measure the vertical height distance in meters. We will step on the scale and get our weight. 2c. We will use a meter stick and a force platform. 2d. use the formula: Win=GPE compare results to computer generated data. Win=GPE F*d=mgh F(.16)=(63.5)(9.8)(.31) F=1,205.7 N
 * Trial # || Change in Distance (m) || Vertical Height (m) || Weight ||
 * Trial 1 || .16 || .31 || 63.5 ||

FORCE PLATFORM RESULTS: Weight: 646.81N Force: 1,255.04N

Percent Error: (Force calc-Force exp)/(Calc. Force)*100 1,255.04-1,205.7/646 *100 Percent Error=7.6%

1/9/11 **Summary**: EPE comes from the bending of the knees. GPE and kinetic energy occur afterwards as you head into the air. The amount of energy is equal at all positions. The greater the vertical distance, the greater the GPE.
 * Physics Talk**

Jumping on a trampoline is different. The potential energy from the height your jumping would provide kinetic energy when landing. You are losing GPE at the same time. Due to the EPE of the trampoline, it can bend and stretch, and bounce you back up. The springs gain EPE which changes to KE then to GPE.

1. EPE allows for this to happen when bending the knees, and getting ready to launch. By the bending of the knees, the muscles are contracting and getting ready to spring up when launching. 2. During the launch, the student would gain kinetic and gravitational potential energy. The peak would be GPE. 3. Sound energy, electrical energy, and chemical energy.
 * Checking Up **

1/10/11 1. W=F*d W=(50)(9.8)*1 W=490J 2. Work (in) starts it off with the push of the bobsled, plus the GPE, then it gains kinetic energy, and work out ends it when it breaks. 3. A frame by frame (slow motion) can display this. There is no such thing as hang time. No person can defy gravity. The maximum heights do change during each frame with some displacement in between. 4. The person who is making a claim should prove that it is so. You can't just say whatever is true without evidence. You have to prove the fact with an experiment. 5. How to change max. jump height: Bend as slow as you can, and jump up. You want to reduce your body mass without muscles. Increase the force of the jump by bending more, but going too low can be bad. 6. W=F*d 6a. 1*1= 1J 6b. 1*10=10J 6c. 10*1=10J 6d. .1*100= 10J 6e. 100*.1= 10J 7. They are the same as above because of the law of conservation of energy. 8. These answers are the same as 6 as well because of the law of conservation of energy. 9. W=f*d W=50(43)=2,150J
 * PTG**

10. KE=1/2mv^2 KE=1/2(62)(8.2)^2 KE=2,084.4J

11a. F=ma 30=(5)(a) a=6m/s/s 11b. W=F*d W=30(18.75) W= 562.5J

12a. W=F*d 40,000=3200(d) d= 12.5 m 12b. F=ma 3200=(1200)(a) a=2.7 m/s/s

13. KEi=Wout 1/2mv^2=F*d 1/2)(.15)(40^2)= Wout 120J=Wout

14. Win=KEf F*d=1/2mv^2 417d=1/2(64)(15)^2 d=17.3 m

15. Pole Vault: KE when running > EPE bend of the pole > GPE is the max. height > KE when about to land > Work from cushion on fall *Not on ground because the cushion is above the ground.
 * || KE || GPE || EPE || SUM ||
 * Running || 20 || 0 || 0 || 20J ||
 * Full Bend of Pole || 4 || 0 || 16 || 20J ||
 * Peak Height || 0 || 20 || 0 || 20J ||
 * Landing || 2 || 18 || 0 || 20J ||
 * Collapse || 0 || 20 || 0 || 0J ||

16. Trampoline: GPE at max. height > KE when about to land on trampoline > EPE when hitting tramp. surface and going back up 17. Skiing: top of the mountain is GPE > during the run is KE > at the bottom is work when stopping 18. John Smith steps up to the plate, with confidence to hit a homerun and send his team to the championship. He is a power hitter, and hits the ball with a lot of work. The ball gains kinetic energy, reaching GPE a max height after 5 seconds. The ball carries, and carries, and goes out of the park! Homerun! The NEWTONS win!
 * || KE || GPE || EPE || SUM ||
 * Peak Height || 0 || 20 || 0 || 20J ||
 * Landing || 2 || 18 || 0 || 20J ||
 * Lowest Height || 0 || 0 || 20 || 20J ||
 * || KE || GPE || EPE || SUM ||
 * Top || 0 || 20 || 0 || 20J ||
 * Middle || 10 || 10 || 0 || 20J ||
 * Bottom || 20 || 0 || 0 || 20J ||

1/10/11 1. GPEi=KEf+GPEf mgh=1/2mv^2+mgh (9.8)(50)=1/2(v^2)+(9.8)(30) 490=1/2v^2+294 v^2=392 v=19.8m/s 1b. Mass can cancel because it is in every part of the problem (GPE and KE in this instance) and any number wouldn't affect the final result.
 * Physics Plus**

2. GPEi+EPEi=KEf mgh+1/2kx^2=1/2mv^2 (.3)(9.8)(2)+1/2(60)(.4)^2=1/2(.3)(v)^2 10.68=.15v^2 v=8.4m/s

3. GPEi+Win=KEf+GPEf+Wout mgh+F*d=1/2mv^2+mgh+F*d (200)(9.8)(25)+200,000=1/2(200)(40)^2+20(9.8)(h)+50,000 249,000=160,000+1960h+50,000 h=19.9m

1/10/11 Hang time does not exist, and therefore, it does not defy gravity for some people. Gravity (9.8) is a constant number on earth, and is the same for everybody, even if you are a premier athlete. This can be showed in various frames of a slow motion video for example, by marking off the feet, showing the displacement (changes in distance) of the feet. A world-class figure skater cannot defy gravity either. She may jump higher than other times, but she can not remain in the air for hang time. If the maximum height were to change, it would not be by very much.
 * What Do You Think Now?**