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Chapter 2

Section 1
toc __http://espn.go.com/nhl/recap?gameId=301107013__ My article is about a NHL hockey game. In which one team shut out the other. The physics is applied to this sport by skating, shooting, and reaction times. Skating applies to physics because the friction of the metal on the skate allows the player to change direction. Shooting has to do with physics becuase the force of the stick hitting the puck makes it go in that direction in a certain velocity. Last, reaction times have to do with the goalie. Their reaction time is very important for them to react to make the save.
 * __Physics Article__**

In this picture, I see a group of people playing soccer. It shows three people running, but the one in the back looks as if he is running very fast. One of the kids who is running kicks the ball really far, while the one standing still barely kicked the ball anywhere. I also see a lady bug trying to push the ball as well as mouse. Both of these animals are not moving it. When a figure skater is moving across the ice at a high speed with no effort, it is caused by momentum which is brought on by their mass and velocity. The same goes for a soccer ball when it is rolling across afield after being kicked. The force of the foot kicking the ball accelerates it to a certain velocity, the momentum of the ball allows it to keep rolling.
 * What Do You See/What do you think? Section 1**

2a. 5.25 m. b. The skater will go back and forth but will gradually decrease his height as time goes goes on. 3a.The result was 6.03 m. The prediction wasn't completely off, but it was close. Also as time went on, the height of the skater did not decrease or increase. b. The ball remains constant in its maximum height. 4a. Our prediction is that, the maximum height of the ball will be less than its maximum height with a steeper slope. Measurement prediction: 5.50 m. b. The result is 5.08 m. Our prediction was very close because we predicted the maximum slope to be less than when it had a steep slope. The second result is 4.41 m. Still proving our prediction to be correct. 5a. No because there is no slope to give the skater the necessary momentum to bring him back to max height. He will simply fall of the slope. b. We predict it will take 100 m. for the skater to stop. c. The thing to keep the skater rolling on the track is to have absolutely no friction to allow him to stop. d. The skater does not stop rolling no matter how long the horizontal track is. 6a. The other side of the track is elongated. b. The max height also decreases with a less steep slope. c. They are usually about equal if the slope on each side is equal. d. The skate would not stop if there was a horizontal slope. If there was not a horizontal slope, he would go back in the other direction.
 * Investigate**

- Inertia is a property of matter - Inertia measures the resistance to changes in an object's motion - Mass is how to measure Inertia - Weight is how much gravity pulls on a mass - The greater the mass, the greater the inertia. - Kg. is used to measure mass - A running start allows one to create more force to react on the object to create a greater velocity - Frame of Reference: a vantage point with respect to which position and motion may be described.
 * Physics Talk Summary**

1. Inertia is a property that measures the resistance to changes in an object's motion. 2. An object will not change their motion unless it is forced to. 3. Friction is needed to stop a ball from moving at constant speed. 4. Friction is needed to stop a ball from rolling in the real world. 5. The object with the greater mass will have a greater inertia. 6. It is important because it is relative to the train.
 * Checking Up Questions**

1a. The ball will keep on rolling because there is no friction to make it stop. b. Newton's First Law of Motion supports this because it states that an object will not change their motion unless it is forced to. 2. The second height it will reach is also 20 cm. 3. It is not possible because friction will cause an object to stop rolling at some point. 4. The instant the puck leaves the stick, the force applied on the puck creates a certain velocity. This velocity is then added onto the velocity of the hockey players motion. The puck will go this speed, until it hits something then i will change direction. 5. 2.5 + 4.5= 7 m/s 6. 10.3 + 4.2= 14.5 m/s 7a. 5.6 + 2.4= 8 m/s b. 5.6 - 2.4= 3.2 m/s c. 6.1 m/s at 23 degrees form the trains direction. 8. 85 - 18= 67 m/s 9a. 21.2 cm b. 43.9 cm c. 58 cm d. 172.1 cm __Work__ 10a. Throwing a javelin, shooting a puck, and kicking a soccerball. b. The javelin thrower was able to throw the javelin that far due to his perfect way of getting a running start. His running start allowed him to get the javelin up to his speed, then when he threw it, the speed of the javelin being thrown is added to the speed of the thrower to create a nice toss. The hockey player shot the puck from the blue line with enough force to allow it to get up to a velocity of 8 m/s. This was generated form the force of the players stick shooting the puck. What a goal from Landon Donovan! He gets a nice running start on the penalty shot to allow the ball at rest to go fast enough to get by the goalie.
 * Physics To Go**

Figure skaters are able to keep moving across the ice at high speeds along with a soccer ball continuing to roll because of their horizontal speeds. This is determined by their inertia, which is mass and velocity. Both of these factors are what allows objects to continue moving for a little while.
 * What do you think now?**

Section 2
In this picture I see a kid walking behind a dog very slowly. The dog and the kid must be walking slow because the footsteps are close together. The bottom of the picture shows the same kid but he is sprinting after the dog. The footsteps are much farther apart in this picture. The meaning of 100 mi/h and 45 m/s shows the velocity of the ball being released by the pitcher. It also has to do with how much time the batter has to react to the pitch.
 * What do you See/Think?**

- Average Speed: v=d/t - instantaneous speed is your speed at that moment - Acceleration is the change in speed divided by the change in time or time elapsed. a=v/t - The units for acceleration is m/s/s or m/s^2
 * Physics Talk**

1a. At constant speed, the distance between the dots should be exactly the same. b. Positive acceleration should show the distance between the dots increasing as time elapses. c. Negative acceleration should show the distance between the dots decreasing as time elapses. 2. v=d/t--->v=400/50--->v=8 m/s 3. Instantaneous speed is ones speed at that moment, while average speed is the distance traveled divided by the time it took. 4. a=v/t--->a=100/10--->a= 10 m/s^2
 * Checking Up**

1. 2. 3a. The acceleration is at -5 m/s^2 b. -5m/s^2 c. 5 m/s^2
 * Physics Plus**

1. Instantaneous speed is ones speed at that moment, while average speed is the distance traveled divided by the time it took. 2a. v=d/t--->v=1000/15--->v=66.7 m/s b. v=d/t--->v=84/6--->v=14 m/s c. v=d/t--->v=9.6/2--->v=4.8 km/hr d. v=d/t--->v=400/4.5--->v=88.9 km/hr 3a. Yes (positive) b. Yes (positive) c. No d. Yes (negative) e. No f. No 4a. Constant increase: Graph A,D b. Constant speed: Graph B c. Greatest change in speed: Graph A d. Increase then decrease: Graph C e. A: Increase, B: none, C: Increase then Decrease, D: Increase 6a. a=v/t--->a=-12.5/9--->a=-1.36 m/s^2 b. Negative value because it decreased in speed. 7a. Constant speed b. Positive acceleration c. Constant, Positive acceleration, negative acceleration d. Constant, negative acceleration, positive acceleration 8. v=d/t--->v=100/2--->v=50 mi/h 9. No this does not mean their instantaneous speed was always 15 m/s. Average only means that was the speed during the time elapsed. 10. x x x x x x x x x x 11. 14a. Constant motion at an average speed would be a track athlete running the mile. b. Constant motion at a fast speed would be a sprinter. c. Constant motion at a slow speed would be a wrestler d. Positive acceleration would be a pitcher throwing a baseball. e. Negative acceleration would be a NASCAR driver stopping at the pit.
 * PTG**

In my words, 100 mi/h and 45 m/s have many different possible descriptions. This can be an average speed where it is the total distance divided by the time elapsed, or it can be an instantaneous speed. This would mean that is the objects sped at that very second. Both of these are different in a sense, but also can be the same. The instantaneous speed can equal the average speed, if the speed was constant the entire time.
 * What do you think Now?**

The sport I chose to explain is golf, when a golfer drives the ball off the tee. When a golfer lines up to drive the ball, the ball is at rest. As soon as they hit the ball, the golf ball has a positive acceleration. The ball will travel at a constant speed for a little until the air resistance and gravity cause it to slow down. In this case, it would be negative acceleration. This ball will land and roll until it finally stops.
 * Reflecting on the Section/Challenge**

Section 3

 * What do you see/think?**

In this picture, they show a person going from a slow velocity to a high velocity. This person is pushing a ball with a stick as well. A force can be a push or a pull factor. They will both have the same amount of force however, the tennis ball will move faster than the bowling ball.

- Acceleration equals force divided by mass - Force equals mass times acceleration - Mass equals Force divided by acceleration - Newtons Second Law of Motion: Putting force on an object with a small mass creates a high acceleration. - Gravity is an unbalanced force that creates acceleration when an object is dropped - Weight equals mass times gravity. (Gravity=4.9 m/s^2) - One force acting on an object causes acceleration
 * Physics Talk**

1. Newtons second law of motion in my words is an unbalanced force causes acceleration. 2. Increasing the objects mass will cause the acceleration to decrease. 3. From knowing the object is 30 N, you can infer that the acceleration is 30 m/s^2. The mass would be 1 kg. 4. Your weight would increase due to a greater gravity.
 * Checking Up**

This physics plus was about Newton's Second Law of Motion. This law talks about acceleration due to unbalanced forces. One unbalanced force is gravity. Whenever there is a projectile, gravity always has an acceleration of -9.8 m/s^2. Using the equation w=mg, w stands for weight, m stands for mass, and g stands for acceleration due to gravity. The weight of an object is directly proportional to its mass. Free body diagrams are also used to show what direction an object is acceleration. Mass always stays the same, while weight changes due to gravity.
 * Physics Plus**

1. 125N north, 125N west: a^2+b^2=c^2--->25^2+125^2=c^2--->c=176.8 N 2a. Player A=40 N north. Player B=70 N south; 70N-40N= 30 N south 2b. 70N south - 40N north=30N south---> a^2+b^2=c^2--->30^2 + 40^2=c^2--->2500=c^2--->c=50N SW 2c. It is southwest


 * PTG**

1a. F=ma---> 70 kg x 5 m/s^2 = 350 N b. m=F/a---> 800 N / 10 m/s^2 = 80 kg c. a=F/m---> 70 N / 7 kg = 10 m/s^2 d. m=F/a---> 400 N / 5 m/s^2 = 80 kg e. m=F/a---> -1500 N / 100 kg = -15m/s^2 f. F=ma---> 100 kg x -30 m/s^2 = 3000 N 3. a = F/m---> a=42 n/ .30 kg = 140 m/s^2 4. a = F/m---> 20= F/ 0.040= .8 N 5a. A baseball is easier to catch than a bowling ball due to Newton's First Law of Motion. The mass of the bowling ball is much greater, making it necessary for a much greater unbalanced for to stop it than a baseball. b. A baseball is much easier to throw than a baseball because it requires much less of a force to accelerate than a bowling ball. This supports Newton's Second Law of Motion. 9. The force of your hand acting on the ball is stopped immediately after your hand is no longer touching the ball. 10. The unbalanced forces are the two people pushing the desk. The total force in this situation is 90 N. 11. 200 N x 4= 800 N 12. a= F/m--->a= 125 N/.7 kg = 179 m/s^2 13. a^2+b^2=c^2--->50^2+120^=c^2--->c= 130 N @ 67 degrees NE 14. a^2+b^2=c^2--->4000^2+5000^2=c^2--->c= 6403 N @ 53 degrees NE 15. F= am--->F = 12.8 kg x 9.8 m/s^2--->F = 125 N 16a. a^2+b^2=c^2--->30^2+40^2=c^2--->c= 50 N at 53 degrees b. a = F/m--->a= 10/5.6--->a= 1.8 m/s^2 17a. a^2+b^2=c^2--->30^2+20^2=c2--->c=36 N at 34 degrees b. a= F/m--->a= 34/100--->a= .36 m/s^2 c. a= F/m--->a= 50/100--->a= .5 m/s^2 18. Stephen Strasburg exerts 200 N of force on a 0.15 kg baseball to cause it to travel 101 mph. The batter does not have a quick enough reaction time to exert enough force necessary to make the bat accelerate quick enough. The ball is then caught in the catchers mitt where it comes to a complete stop.

If you were to apply the same amount of force on a tennis ball and a bowling ball, they would both move at a very different speed. This can be determined using Newtons Second Law of Motion, where F=ma. It requires a much smaller amount of force to allow the light tennis ball to accelerate. If this same force was applied to the bowling ball, it will move at a much smaller velocity due to a small acceleration.
 * What do you think now?**

Section 4
In this picture I see a boy sitting in a chair with two heads. There is also a girl standing on top of a stool dropping an apple in one hand, and throwing one with the other. I think that the amount of force applied to an object and its velocity is how one would determine how long it travels in the air before dropping.
 * What do you see/think?**

Trajectory- Path. Projectile- An objected acted on only by gravity. The x-component and y-component of all vectors are independent. Vertical velocity affects vertical distances, while horizontal affects horizontal. The time for a horizontally launched projectile to hit the ground is the same as the time it takes to drop. Acceleration due to gravity is -9.8 m/s^2. Horizontal velocity does not change for a projectile. Throwing horizontally results in the same trajectory as the second half of a ball thrown at an angle.
 * Physics Talk**

1. They fall at the same time because they are dropped at the same height and have the same acceleration. 2. It increases about 10 meters every second. 3. The point of highest rise is zero and the acceleration is -9.8 m/s^2
 * Checking Up**

1a. 2.
 * Physics Plus**
 * t (s) || x (m/s) || y (m/s) ||
 * 1 || 10 || 20.2 ||
 * 2 || 10 || 10.4 ||
 * 3 || 10 || 0.6 ||
 * 4 || 10 || -9.2 ||
 * 5 || 10 || -19 ||
 * 6 || 10 || -28.8 ||

1/2. 4. Everyone that was asked said that the bullet shot horizontally will hit the ground after the one that is dropped. They say this because it will take longer to hit the ground due to the horizontal speed of the bullet, however when tested they will actually hit the ground at the same time. 6. Horizontal and vertical motion both have no effect on each other because horizontal acceleration is always zero, while vertical acceleration is always -9.8 m/s^2 due to gravity. 7. Due to gravity and no air resistance, both of the arrows will hit the ground at the same exact time. 8. 3.6 m/s @ 33.7 degrees 9a. 12 m/s b. 24 m 10a. 8.5 m/s b. 4.25 m 11. And Phil Hughes deals the pitch at 95 mph. The batter hits the 0.15 kg ball with 200 N of force with a velocity of 30 m/s at 30 degrees. The horizontal acceleration of the ball is at zero, while the gravity effects the vertical motion with an acceleration of -9.8 m/s^2. The ball reaches its max height then begins to drop down until it lands in the outfielder's mitt.
 * PTG**

http://www.youtube.com/watch?v=zmFrZeTGnyQ This video shows the independence of vertical and horizontal motion due to a fly ball hit by the batter. The vertical motion has a acceleration of -9.8 m/s^2, while the horizontal acceleration is always 0. The trajectory is shown with object traveling upwards, then when it reaches its maximum height, it goes down in a symmetrical path as its way up. The shape of the trajectory can play a role in the game, that if the range of the trajectory is very long, this means the baseball was hit far.
 * Reflecting on the Section**

The factor that determines how far an object travels when it thrown has to do with it x and y components. First, it depends on the angle the object is thrown and at what initial speed. Using sin and cos, you can then determine the initial horizontal and vertical speeds. Next, the acceleration also plays a role in this, where the horizontal acceleration is always zero, and the vertical acceleration is -9.8 m/s^2 due to gravity. Using the equation d=vi(t) + 1/2(a)t^2, you can determine the horizontal distance at a certain time.
 * What do you think now?**

Section 5
In this picture, I see a girl who looks as if she just kicked the ball, then the ball was headed into the net passed the goalie.The angle of a trajectory can be described in a few ways. It can be launched at a high angle, where the max point would be higher than if was launched at a lower angle. Also, a greater launch speed would increase the range because it would travel longer in the air.
 * What do you see/think?**

- Downward acceleration is -9.8 m/s^2 due to gravity - If you were to ignore air resistance, the path of the trajectory would be a parabola - No matter what angle the ball is launched, its path is a parabola - A 45 degree angle always produces the greatest range - Smaller angles have a greater horizontal velocity, but are in the air a shorter amount of time - The range is equal for 10 degrees and 80, 20/70, and 30/60 - A model shows the trajectory path when a ball or object is launched
 * Physics Talk Summary**

1. The two types of motion for a trajectory is its vertical motion and horizontal motion. 2. The model would be accepted if it matches reality in nature. 3. The closer the angle is to 45 degrees, causes a greater range. The farther away it is causes a smaller range.
 * Checking Up**

The various angles of a trajectory effect the projectile's path. The closer the angle is to 45 degrees means the greater the range. At times, you can launch a projectile at a different angle and have the same range. This would be because whenever two angles are complimentary, they create the same range.
 * What do you think now?**


 * Physics Plus**

1. The angle of 45 degrees produces the greatest range 45 +45 makes a complimentary angle. 2a. The hang time is greater when the angle is above 45 degrees. b. The hang time is shorter when the angle is below 45 degrees. 3a. 30 degrees is equal to 60 degrees b. 15 degrees is equal to 75 degrees 4. The longer jumper will have a short hang time and will have a small range. 5. He is successful in both because he has a fast velocity along with a 45 degree angle of a jump, allowing him to jump very far. 6a. The acceleration is -9.8 m/s^2 due to gravity b. The horizontal velocity is the same as the launch speed, and the vertical velocity is 0. 7a. 29.4 m/s b. Horizontal speed at 1 second is still 5 m/s c. The diver reaches the water 15 m from the cliff b. 5 m/s c. d=Vi x t--->d=(5)(3)--->d= 15 m. 8. 45 degrees creates the longest range. 9. Throwing the ball 90 degrees would create the greatest height. 10a. It accelerates down b. d=vit+1/2at^2--->-100=-4.9t^2--->t=4.5 seconds c. d=vit+1/2at^2--->d=20(4.5) + .5(0)(4.5)^2--->d=90 m.
 * PTG**

Section 6
In this picture a kid is sitting on a roll chair with a helmet on. The first segment shows the kid hitting the wall with his feet and the other shows him pushing off. In the picture, it also shows that when he is pushing into the wall it bends, but when he pushes off it moves outward. If I were to give advice to someone who has never jumped, I would tell them to squat down then push up using the force of their feet against the ground.
 * What do you see/think?**

- When walking pushing your feet backward causes you to accelerate forward - Forces are always identical when acting upon each other - Newtons Third Law: For every applied force, there is an equal and opposite force. The two forces always act on different objects - Forces are opposite and equal - The upward angle of the meter stick is the force being applied back to the mass on it - If the floor was not applying force back, you would fall right through it - A free body diagram is used to show the relative strength and direction of all the forces acting on an object in a given situation - The size of each arrow shows the strength of force - w=mg
 * Physics Talk Summary**

1. Newtons third law states that for every force of object A, object B has an opposite and equal force. 2. Earth pulls down on the mass with a force of gravity and the mass pulls up on Earth with an equal force of gravity. 3. A free body diagram illustrates the strength and direction of all forces acting on an object in a given situation.
 * Checking Up**

1. Yes the ball exerts the same amount of opposite force due to Newtons Third Law of Motion. 2. The chair exerts an equal but opposite force on the person sitting. The chair is strong enough to do this so it prevents it from breaking. The deflection would only be seen if the person weighed A LOT however. 3. A bathroom scale works by using the equation w=mg. Where the mass of the person times the gravity equals the weight, or force being applied on the scale. 4. The force of the bat on the ball is equal but opposite to the force of the ball on the bat. When a bat hits a ball, there is a deflection on the bat. When the force is too great, the deflection becomes to great for the bat to bend, so it snaps. 5. A linebacker would apply more force than the running back, causing the running back to fall backward and the linebacker to continue forward. 6. When a hockey player hits the boards, the boards deflect and apply the same amount of force back on the player. 7. A baseball player uses a glove in order to catch a baseball because the hand will apply force on the glove, which applies force on the ball to catch it. All in an equal but opposite force. The glove reduces the force of the ball hitting the hand. 8a. Parise skates up the ice and takes a hard slap shot. Ohhhh and it rattles off the post. The puck hits the post with a high velocity and high force, but the post also exerts an equal but opposite force back, causing it to fly off the post at a high speed. b. Deflection of the ground could cause force because jumping on such as a trampoline, causes one to jump higher since there is a great opposite force. This could help make a commentary more interesting by having a high jumper jump much higher if we pretended it was off a deflecting ground.
 * PTG**

If i were to meet someone who has never jumped, I would tell them to apply as much force as possible against the floor. The floor will then apply the same amount of force in the opposite direction. This supports Newton's Third Law of Motion, and following the standard of applying as much force as possible to the floor, allows a higher jump.
 * What do you think now?**

Section 7
In the first segment of a picture a kid has a spring scale attached to a shoe, this shoe seems to be moving very easily since it is on ice. In the other segment, he is doing the same thing but on sand, he appears to be having much more trouble though. Some sports require different shoes because it needs more friction and force to create a faster velocity.
 * What do you see/think?**

- Constant velocity occurs when there is no net force - The second force of the shoe sliding on a surface is friction - The force forward and the force of the friction in the opposite direction allows a constant speed - The vertical forces on the shoe add up to zero as well because the downward force of gravity is equal to the upward force applied by the shoe surface - Force applied perpendicularly to a surface is called normal force - The coefficient of sliding friction is the force of friction divided by the perpendicular force exerted by the force on the object - This has no units - expressed in decimal form
 * Physics Talk Summary**

1. They are both equal because in order for the shoe to move at constant speed, the force forward must equal the force backward. 2. The coefficient of friction has no units because it is a force divided by a force 3. The coefficient of friction is determined by the force of friction divided by the perpendicular force exerted by the force on the object
 * Checking Up**

1. A sport where weather conditions that would cause an athlete to wanter more friction would be track. If the track is wet, the runner would want to have track shoes with good spikes on the bottom so he or she can get more friction. 2. Hockey is a sport where the athlete wants little friction, this is so they can skate at high speeds without stopping from friction. This is done by sharpening their blades often in order to reduce friction. 3. Another court may differ in friction due to its surface. She will need to know the surface's material of the other court in order to find out how the shoes will react on it. 4. They do not change shoes because a hard surface provides a regular friction, clay provides a lot of friction, and grass courts have very thin grass allowing it to be easy to create friction. 5. 0.03=x/600--->x=18 Newtons of force 6a. w=mg--->w=(1000)(9.8)---> w= 9800 N b. µ=f/N--->0.55=f/9800--->f= 5390 N c. -f=ma--->-5390=1000a--->a=-5.39 m/s^2 d. Vf=Vi + at--->0=Vi +(-5.39)(6)--->Vi=32.34 m/s. The driver was not telling the truth. e. The original speed of the car was 32.34 m/s, this number means the driver was not telling the truth of his 29 m/s claim. 7. Air resistance and water resistance increases as the speed increases because it requires a greater opposite force. 8. A maximum force does have a limit on how fast one can accelerate no matter how strong. In order to solve this problem, the friction must be reduced. This can be done by buying new shoes that are smoother on the bottom to reduce friction. 10. Friction is important when running because friction is what allows someone to run without falling. Football and soccer both need cleats because they create more friction on the surface. If regular shoes were used during these sports and baseball, there would not be enough friction and people would keep slipping. 11. What a hit! The ball drops in the gap and Bob rounds first and second. The outfielder drops the ball and picks it up, Bob goes to round third but he slips and falls then gets tagged out. He slipped because the spikes on his cleats are worn out, not allowing enough friction between his foot and the ground to keep him from slipping.
 * PTG**


 * Physics Plus**


 * Lab**
 * Tension(N) || Tension(N) || Tension(N) || NFf(N) || Total Weight(N) || Mu || Class Avg. Mu || %Difference ||
 * 0.5 N || 0.5 N || 0.5 N || 0.5 N || 1.4 N || 0.36 || 0.325 || 10.77% ||

Fx=max--->-f=max--->-.65196=.18477a--->a=-3.53 m/s^2 Fy=may--->N-W=may--->N=W--->N=mg--->N=(.18477)(9.8)--->N= 1.811 N __Formula used for initial velocity__ Vf^2=Vi^2 + 2ad--->0=Vi^2 + 2(-3.53)(7.94)--->Vi=7.49 m/s __Formula Used fpr Calculated Time__ Vf=Vi + at--->0=7.94 + -3.53t--->t= 2.12 s µ=f/N--->0.36=f/1.811--->f=.65196 N __Percent Error Formula__
 * Mass(g) || Mass(kg) || Measured Time(s) || Measured Distance(m) || Ff(N) || Acceleration(m/s^2) || Calculated Vi (m/s) || Calculated Time (s) || %error ||
 * 184.77 || 0.18477 || 1.96 || 7.94 || 0.504 ||  || 7.49 || 2.12 || 8.16% ||
 * 184.77 || 0.18477 || 1.90 || 8.10 || 0.504 ||  || 7.56 || 2.14 || 12.63% ||
 * 184.77 || 0.18477 || 1.84 || 8.05 || 0.504 ||  || 7.54 || 2.13 || 15.76% ||
 * 2.12-1.96|/1.96 x 100--->8.16%

1. The coefficient of friction shows the friction between the block and the surface of the floor. 2. My calculation for µ was 0.36 and the classes' was 0.325. The results varied because of the way people read the spring scale. 3. My percent error varied, but the average was about 12.18%. This is pretty decent percent error. 4. Theoretical means it applies to the real world, what we tested and our results. This displays Newtons' Laws because friction is the unbalanced force. 5. Some things such as using a different surface, failure to stop the clock at the right time or start it, or releasing the block at the zero mark of the tape.

Some sports require special shoes because in order to get more traction, it requires a greater friction. Thus the sliding friction would increase if the shoes' material was had more traction. Such as cleats on dirt, the spikes on the cleats create a greater friction that shoes on dirt. If the sliding friction was very small, then the person would slip. Without friction, it is impossible to walk.
 * What do you think now?**

Section 8
In this picture I see a person accelerating very quickly with a long pole in her hands. She presses the pole against the ground to allow herself to shoot up in the air to a height of twenty feet. The reason why they may not be able to attain a height of 12 meters may be due to a lack of speed from the pole vaulter. Velocity should be the main variable in order to attain a certain height.
 * What do you see/think?**

- A force acting on an object that can change position and speed - A ball traveling vertically in the air with a certain speed will have the same speed when it reaches the same height were the force was applied - Kinetic Energy: Energy with motion - Gravitational Potential Energy: Energy associated with position - Potential Energy: Total Energy - Any force acting on an object changes energy from one form to another - The concept that total energy remains constant is the law of conservation of energy - Work is a force applied multiplied by the distance - Elastic Potential Energy is when an object bends, such as a pole vaulter to propel them higher - When an object reaches their max height, Gravitational Potential Energy is what the energy changes to - W= Fd - EPE=1/2kx^2 - GPE=mgh - KE=1/2mv^2 - Joules are the units for energy
 * Physics Talk**

1. A force is required to change the energy of an object 2. The penny that is launched in the air gets its energy from EPE of the ruler 3. The pole vaulter gets the energy from his kinetic energy transfered to the EPE 4. Work uses Force(N) and distance(m). Kinetic energy uses mass(kg) and velocity(m/s). GPE uses mass(g), gravity(m/s^2), and height(m). EPE uses k as the spring constant(N/m) and x as the deflection(m).
 * Checking Up**

The reason why they cannot achieve the height is because of the person's insufficient speed. Using energy conservation, the Kinetic Energy would transfer to Gravitational potential energy. The velocity of the pole vaulter needs to be quick enough in order to transfer this kinetic energy into a greater height.
 * What do you think now?**

1. Work to push the shot-put a certain distance changes to kinetic energy which changes to GPE at max height, which then changes to KE on the way down. 2. Elastic potential energy to kinetic energy while winding back, work to move forward, kinetic energy transfers to the ball, GPE at max height, KE on the way down. 3. KE=GPE 1/2mv^2=mgh 1/2m(12)^2=m(9.8)h 72=9.8h h=7.3 m 4. The limiting factor is for a pole vaulter is initial speed to create a high kinetic energy. Height is not involved in KE. 5. My prediction is that her initial speed was very fast in order to create a high jump due to the KE.
 * PTG**

6. KE=GPE 1/2mv^2=m(9.8)(4.55) 1/2v^2=44.59 v=9.5 m/s

7. If he jumped higher, the initial speed must have been higher also KE=GPE 1/2v^2=(9.8)(6.14) v= 10.97m/s

8a. GPE=KE (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 because the mass cancels out on both sides of the equation. This states that work will not be necessary because without friction there is no work being done on the rock to stop.

9a. W=EPE W=1/2kx^2 W=1/2(1500)(.25)^2 W=46.88J

9b. EPE=KE 46.88=1/2mv^2 46.88=1/2(.1)v^2 v=30.6m/s

10a. EPE=W 1/2kx^2=Fd 1/2(315)(.3)^2=W W=14.2J

10b. W=Fd 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) Nm= J 12c. KE=1/2mv^2 ; 1/2(kg)(m/s)^2 ; 1kg x 1 m/s^2 = J; kgm/s^2m=Nm 12d. EPE = 1/2kx^2 ; 1/2(Nm)(m)^2; Nm 13. EPE of the bend in the board transfers to KE, which transfers to GPE at max height. 14. EPE in bending the arm back transfers to W to reach the ball, which transfers to KE of the ball, and then transfers to GPE at max height. 15. The wind up and pitch, the batter does work to by swinging the bat, the ball is smacked from transferring all that work into KE. The ball reaches its max height with a high GPE. This ball is outta here. 16. The Law of Conservation fo energy applies to baseball and softball by transferring the energy in work, to KE of the ball, to GPE at max height. all of these have equal total energy.

Section 9
In this picture I see a figure skater jumping high in the air while spinning. There is also a helicopter next to the skater with someone holding a timer inside of it. Hang time of athletes do not defy the laws of gravity. Everyone has a constant pull from gravity at all times. Even a world class figure skater does not defy the laws of gravity. They must have a certain technique when they jump to get high enough to perform a triple axel.
 * What do you see/think?**

-The energy of the a jump must be equal at all stages of the jump - The higher one jumps, the more GPE they have - In a system with no external forces, the energy at one point must be equal to the energy at another point - All of this supports the conserving of energy in the law of conservation of energy
 * Physics Talk**

1. The energy comes from the work in the distance of the crouch position to the ready position 2. The launch position has both KE and GPE, at the max height it has GPE 3. Other examples of energy are light energy, chemical energy, and nuclear energy.
 * Checking Up**

Prelab Activity: 2. 20 frames 3. 2/3 second 4. Yes, at max height 5. 1 second
 * Investigate**

Lab 1. Sequence A: Bent knees--->Unbent knees--->Sequence B: Airborne. W=GPE 2a. The amount of energy in unbending your knees b. The data recorded will be the force to push off the ground, hang time, height of jump, and distance of bend in knees c. Meter stick, force platform d. Run trials, a partner will measure the height of the person, the distance they bend, and the distance they jump. 3. MY JUMP: GREEN
 * My height(m) || Bend(m) || Height jumped(m) || Mass(kg) ||
 * 1.88 || 0.56 || 0.6 || 86 ||

W=GPE Fd=mgh .56F=(86)(9.8)(1.16) F=1745.8 N 4. Using the force platform my force was 2660.68 N 5. My calculation was significantly less than the actual force Percent Error: %error=|calc-exp|/calc x 100 %error=|1745.8-2660.68|/1745.8 x 100 %error=52.4% A reason for this very high percent error could be for a few possible reasons. The main one however is the human error in finding the exact height, and bend in the jump. being off by a few centimeters can completely alter the conclusion. Conclusion: This lab showed us how the transfer of energy relates to jumping. We can now infer that the more energy the higher you will jump. The more force exerted into the ground creates a greater max height.

The hang time of any athlete or person does not deft gravity. Gravity is always constant with 9.8 m/s^2. It is possible for an athlete, figure skater, or basketball player to jump higher sometimes, but they never defy gravity because gravity is always acting upon everyone.
 * What do you think now?**

1. W=Fd W=(50)(9.8)1 W=490J 2. Work starts the bobsled, this changes to GPE at the top of the run, this turns into KE of the bobsled going downhill, and work due to friction stops the bobsled. 3. A video in slow motion that goes frame by frame can solve this. The player will not defy gravity, there is no such thing as hang time. 4. The person who is making a claim should prove it that it is possible to defy gravity. They should provide a thorough experiment with accurate results. 5. Two ways to increase max height are a greater bend in their knees when the jump, and a greater velocity. 6. W=Fd a.. 1 x 1= 1J b. 1 x 10=10J c. 10 x 1=10J d. .1 x 100= 10J e. 100 x .1= 10J 7. They would all have the same amount of energy at GPE due to the Law of Conservation of Energy. 8. All of the answers will remain the same. 9. W=Dd W= 50(43) W= 2,150J
 * PTG**

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

11a. F=ma 30=5a a=6m/s^2

b. W=Fd W=(30)(18.75) W= 562.5J

12a. W=Fd 40,000=3200d d= 12.5 m

b. F=ma--->m=3200/9.8 3200=326.5a a=9.8m/s^2

13. KE=W 1/2mv^2=Fd (1/2)(.15)(40^2)= W 120J=W

14. W=KE Fd=1/2mv^2 417d=(1/2)(64)(15)^2 d=17.3 m

15. Pole Vault: KE while running changes to EPE on the pole to GPE at max height to KE on the way down to W from the cushion to break fall.
 * || KE || GPE || EPE || TOTAL ||
 * Running || 100 || 0 || 0 || 100J ||
 * Full Bend of Pole || 20 || 0 || 80 || 100J ||
 * Peak Height || 0 || 100 || 0 || 100J ||
 * Landing || 20 || 80 || 0 || 100J ||
 * Collapse || 0 || 100 || 0 || 100J ||

16. Trampoline: Max height is GPE which changes to KE on the way down and EPE when touching the trampoline again. 17. Skiing: Top of the mountain has GPE to KE on the way down to W to stop at the bottom.
 * || KE || GPE || EPE || SUM ||
 * Peak Height || 0 || 100 || 0 || 100J ||
 * Landing || 30 || 70 || 0 || 100J ||
 * Lowest Height || 0 || 0 || 100 || 100J ||
 * || KE || GPE || EPE || SUM ||
 * Top || 0 || 100 || 0 || 100J ||
 * Middle || 50 || 50 || 0 || 100J ||
 * Bottom || 100 || 0 || 0 || 100J ||

18. With the game on the line, Robinson Cano steps up to the plate. Bard winds up and releases the ball, Cano works his bat around the plate with a high amount of energy, he smacks the ball converting all that work into kinetic energy. This ball is flying to its max height which is now GPE. Seee ya!!!! The yankees win, theeeeee yankees win!

1a. GPE=KE + GPE mgh=1/2mv^2 + mgh (9.8)(50)m=1/2mv^2 + (30)(9.8)m 490m=1/2mv^2 + 294m 196m=1/2mv^2 196=1/2v^2 392=v^2 v=19.8 m/s
 * Physics Plus**

b. It is advantageous because the mass cancels out in the entire equation leaving it with no effect.

2. EPE + GPE=KE 1/2kx^2 + mgh=1/2mv^2 (1/2)(60)(.4)^2 + (.3)(9.8)(2)=(1/2)(.3)v^2 10.68=.15v^2 71.2=v^2 v=8.44 m/s

3. KE=GPE 1/2mv^2=mgh (1/2)(200)(40)^2=(200)(9.8)h 160000=1960h h=81.63 m