home

CHAPTER 2- Mitchell Vinokur

= section 1 =

News article-

The article i found deals with the Physics in Billiards. It explains that when you strike the cue ball, it sents the ball in motion and if it were a flat frictionless surface, the ball would roll forever but because the table has alot of friction and there are sides all around, the ball eventually stops. The article explains that for finess shots, a slow speed is usually better but if you want the ball to go straight then it is better to hit the ball harder. When a ball is hit at another ball, it will stop when it hits that ball and spin for a bit. The energy is transfered, and that other ball then goes into motion. When you hit a ball, the direction it goes is all due to where on the ball you hit the cue. In this part of the game, angles play a major role. A popular shot in pool is called the Center ball. This is when you hit the cue ball dirrectly in the middle and it slides for a bit before starting to spin. This is because slide predominates over role at first. Article From: http://www.jimloy.com/billiard/phys.htm

toc What do you think?

Figure skaters keep moving because of momentum. On ice, you can take a stride and because of the thin blade you can glide on that ice without pushing again because the momentum from your first push is still carrying you.

A soccer ball continues to roll because of momentum as well. Them momentum carries the ball because of the force that had been laid upon it at the time when the player kicked the ball. The ball also has mass which carries the ball into continuously moving.

Investigate

Hypothesis- __**The steeper the initial drop is, the higher the vertical hight will be on the opposite side**__ 1. Initial hight is 7m 1e. 7 m 2a. His point will be the same as the hight of his starting point 2b. Because his slope is steeper so it will carry him until he reaches the hight that he started at.

3a. my prediction was exactly correct 3b. The high at which you start at will be the same as the highest point of where you change directions 4a. I think that he will end up at the same hight again 4b. The prediction was the same as the outcome 5a. No because it would just keep rolling and not stop 5b. Eventually I think he will stop because an object or friction will bring him to a hault 5c. A steep slope and momentum 5d. He kept rolling and went off the track 6a. The length increases 6b. it will still be the same as the initial hight. 6c. it will be exactly the same if there is no friction 6d. he would not stop. He would keep going forever. Conclusion- __**The skater will reach the same hight on the opposite track as where he was dropped from.**__

Physics Talk

Galileo was a scientist who made experiments and figured out that if you release a ball at one hight, it will keep going until it reaches that hight on the opposite track. He also figured out that if a ball rolls on a smooth horizontal surface, it will continue on forever. He came up with inertia which is the natural tendency of an object to remain at rest or continue moving at constant velocity. Galileo figured out that object stop because there are forces like friction that slow it down. Another scientist was Isaac Newton. Newtons first law stated that an object in motion remains in motion and an object at rest remains at rest (without unbalanced forces). Newton also figured out that an objects mass is its inertia. Running starts are important in sports because the speed at which you are traveling and holding an object is the speed that object is traveling during the moment of its release. Therefor, the speed of an object that you are throwing is the sum of all speeds that have to do with you throwing that object. For example if you throw something at 5 mph on a boat that is moving 5 mph then that objects speed would be 10 mph. Frames of refrence are important because they are the angle or perspective at which you see something. To people standing on different surfaces, an object could be moving at a different speed so that is why Frames of referance are important.

Checking up

1. Inertia is natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. 2. Newtons first law of motion says that an object in constant motion will stay in constant motion and an object at rest will remain at rest. This is all depending that there are no forces like friction. 3. Friction or a push/pull needs to act on an object to stop it. 4. Friction stops the motion of the ball because in the real world, nearly everything has friction. 5. The mass that is greater will have the bigger inertia 6. Because to people who are inside the train the ball is traveling at a different speed than people looking on from the platform.

PTG

1a The ball will keep rolling unless a force acts upon it 1b. This shows Newtons law because an object in motion will continue to be in motion. 2. It will reach 20 cm 3. no because in the real world there will always be things such as friction 4. Between the puck and ice, there is little friction so that is why pucks can glide for long periods of time while seemingly loosing very little to no speed. The puck will eventually stop however because there is plenty of forces to stop it inside the rink. 5. He sees the ball go by at 7 m/s 6. 10.3+4.2= 14.5 m/s relative to the ground. 7a. 2.4+5.6= 8 m/s 7b. 5.6-2.4= 3.2 m/s forward 7c. the carts velocity would be 5.6 m/s because moving side to side does not matter 8. 85+18= 103 m/s 9a. sin45 x d= 15cm **d=21.2 cm** 9b. sin 20 X d= 15 cm **d=43.8** 9c. sin15 x d= 15 cm **d=58 cm** 9d. sin5 x d= 15cm **d= 172 cm** 10. The first example is in hockey. When a player hits the puck, it glides on the ice at constant motion. The puck would keep on moving if nothing were to hit it, however in the rink, it is bound to hit something and when it does it will be at rest which demonstrates that an object at rest will remain at rest. The second example would be in bowling. In bowling, the ball glides on the floor and only slows down when it hits a force like pins or the gutter. In a perfect world with no forces such as friction, the ball would roll forever because it has a great inertia and nothing in its way to stop it from doing so. Lastly would be soccer. When a player kicks the ball, it keeps moving at constant speed and in a perfect world it would move forever if no one was to touch it. However someone is bound to touch it and when they do that ball will be at rest.

What do you think now?

Skaters keep moving on ice because between the blade and the ice there is little friction, and when they push, the force carries them intil something slows it down (friction). A Soccer ball continues to roll because when it is kicked, it has inertia and also it keeps rolling until some force stops it.

Inquiring further

Baseball players slide into second base for a number of reasons. One of those reasons is because it is harder for a player to tag you when you are lower to the ground, but in physics terms, people slide into second base because when you slide, you are carrying your momentum unlike if you are running and you just slow down. By sliding you continue the momentum you had when you are running. They often dont slide into first base because you are allowed to overrun first base without being tagged out so if you slide you wouldnt be going as fast as if you kept running through the bag.

=Section 2=

What do you think

100 mph is the speed at which the pitchers can reach. This measurement helps see how effective the pitcher is based on how fast he can throw.

Physics talk

The ticker lab helped us see the distances between ticks based on the kind of motion that was applied. Average Speed can be calculated using As=distance traveled/time elapsed When you are traveling, the exact speed you are going at a certain point is called your instantaneous speed. To calculate acceleration, we use the equation a= change in speed/time interval.

Checking up

1a. the dots would each be the same distance appart because it is constant speed 1b. the spaces would increasingly get farther apart 1c. in negative acceleration, the dots gradually become closer together. 2. 400/50 = 8 m/s 3. instantaneous speed is the speed you are traveling at that exact moment, and average speed is the speed of several sppeds averaged together. 4. vf= vi + at 0= 100 + x10

1. a=vF-vI/ t.... a=-5 m/s - 5 m/s / 1s = -10 m/s^2

Section 3
What do you see?

There is a person who is going faster and faster, while pushing a ball that is staying on a stick.

What do you think?

A force is something that pushes an object and sets it into motion. The harder the force is applied, the faster the object it is hitting will go. If the same amount of force was applied to a bowling ball, it would probably o much slower because the bowling ball has a much bigger mass.

Physics Talk

a=F/m F=ma m=F/a Newtons second law stated that accelerations are caused by unbalanced forces. When the object is small, the acceleration to it is bigger, and vise-versa if the object has a large mass. Due to Newtons law, acceleration of an object can never reach zero. Acceleration is proportional to force but inverse to the mass of that object. Sig Figs- a zero between non-zeros is significant. A zero at the end of a decimal is significant. a zero that starts a decimal is not significant. Unbalanced forces can come in the form of such things such as air resistance, and gravity. Also, there are forces that we apply on objects that are unbalanced and therefor cause acceleration.

Checking up

1. Newtons second law states that accelerations happen because of unbalanced forces such as a push/pull. 2. If you increase the mass of the object, the acceleration is smaller. 3. Because the weight is 30 Newtons, the force is 30 Newtons as well because of gravity. 4. Higher acceleration would cause your weight to increase, but your mass would stay the same because they dont affect eachother.

PTG

1. F1= 350N. m1=800=m x 10= 80kg. a1=10m/s^2 m2= 80 kg. a2=-15. F2=-3000 N

3. F=ma. 42=.30(a)... a=140 m/s^2 4. .F=ma. F=.040(20)... F= .8 N 5a. In newtons first law, he says that an object that is in motion will stay in motion, also a bowling mass has a larger mass than a baseball so it is coming down much harder on you. Because it has more mass, it has more inertia which makes it harder to throw and harder to catch than a beseball. 5b. Newtons second law says that mass and acceleration are directly proportional while Force and acceleration are inversely proportional. Also, since the ball is smaller, it will be accelerating more than the bowling ball. This results in the bowling ball going slower than the baseball. 9. The ball contains the force of your hand until it starts to descend where gravity takes over. 10. 50 + 40=90 N 11. 200 x 4= 800 N 12. 125/.7 (700g=.7kg) 179 m/s^2 13. 130 N Northeast 14. 6403 N 15. F=mg. F=(12.8)(9.8)= 125 N 16a. 50 N @53 Degrees. 16b. a=8.9 m/s^2 17a. 36N at 34 degrees. 17b. .36m/s^2=a 17c. .50 m/s^2 18. as the batter strikes the ball, he hits it with 200 N of force. The ball has a mass of 80 kg. To find the acceleration of the ball after it hits the bat, the eq would look like. 200=80(a). 2.5 m/s^2 would be how fast the ball moves after it hits the bat.

WORK

Physics Plus

1. 125^2 +125^2=c^2. c=176 N 2a. 70-40=30N north 2b. 50N 2c. NW

What do you think now?

Force is something that acts on an object via push or pull. The same amount of force will affect them differently because they have different masses, and therefor will have different accelerations. Because the bowling ball is bigger, will have a smaller acceleration than the lightly massed tennis ball.

=Section 4=

What do you think?

The speed of the object determines how far the object is thrown into the air. As well as the height the object is starting at.

Investigate 1. The hangtime is increased 2. The range is increased as well 3. The time is increased 4. The range is increased 5. The height and the range 6. The hang time and initial speed. Physics talk A projectile is an abject that is acted on only by gravity. There is both an x component and a y component when dealing with trajectory. The y component represents the way the object is moving vertically, and the x component represents the way the object is moving horizontally. When a ball is thrown into the air, vertical velocity is constantly changing. It changes by -9.8 m/s^2 every second. The horizontal velocity however remains constant because there is no force that acts on it horizontally.

Checking up

1. Yes they will land at the same time because mass does not have any affect on this, and since they are dropped at the same time and height, they will land at the same time. 2. No because vertical velocity is always changing by -10 m/s^2 every second. 3. If a ball is thrown upward, its velocity at its highest point is always 0. And the acceleration would be -9.8. PTG 1. ….….. …………. ………….…. …………………

2. …………. ………..……… ……………..……….. ………………..………….

4. Most people think that a bullet that is dropped will hit the ground quicker. It is known that bullets travel extremely fast and a bullet dropped only takes a few seconds befor it hits the ground. However, sience proves that they will hit at the same time because the vertical and horizontal velocities are the same. 6. I believe this statement to be true because no matter how fast you go vertically, the horizontal velocity is still 0, and no matter how fast you go horizontally, the vertical velocity is still changing by -9.8 m/s^2. 7. This is very similar to the bullet problem, they will hit at the same time. 8. 2 km/h up, 3 km/h right. 2^2 + 3^2= 13 (square root of 13= 3.6 tan-1 (2/3) **3.6 m/s @ 33.7 degrees.** 9a. 15 cos 37= 11.98 m/s 9b. 11.98 (2)= 23.96 10a. 12 cos 45= 6.3 10b. 6.3/2= 3.15 11. the pitcher releases the ball at a 40 degree angle. The ball is going 90 m/s, gaining a horizontal velocity of 0, and a vertical velocity of -10 every m/s^2 every second. The ball is then hit into the outfield where its vertical and horizontal velocity are the same as the above in terms of acceleration.

Physics plus #1 and 2



Reflecting on the section [] The angle of the ball being hit would factor into how fast the ball leaves the raquet and they you could find the vertical and horizontal velocity of this tennis shot.

What do you think now? What determines how far an object thrown into the air will travel is a combination of the angle it is thrown, its speed (vertical and horizontal), its hangtime, and gravity or acceleration which is always the same for an x component(0) and always the same for a y component (-9.8).

=Section 5=

What do you think?

Various angles result in various trajectories. If you hit a ball straight on as it is coming down, it will probably go straight up. If you hit it on an angle, it will go more horizontally. The speed may change the range because the faster it goes, the longer and farther it will travel in the air resulting in a larger distance.

Physics talk

A projectile has two motions, one horizontal, and one vertical. Without air resistance, the path of all trajectories are known as parabolas which are bowl shaped curves. Different ranges result from different angles that an object is released from. Degrees adding up to 90 travel the same amount of distance. However, in the real world, air resistance does not make these things happen exactly how they are. The trajectories that are shown in the model have different angles, but the fact that they have the same speed is important as well because if they had different speeds, than the spots in which the objects would be landing would not corespond with eacother.

Checking up

1. The two types of motion are constant speed moving in a straight line, and downward acceleration. 2. In order to have an accurate model, it must match reality in nature. 3. Height and range vary as an angle is increased from 10 degrees to 80 because different angles give you a different range based on how long the ball is in the air and the angle at which it is thrown. However, these angles ad up to 90 so they will land in the same spot.

PTG

1. a 45 degree angle because that is the farthest possible angle. 2a. the amount of time is increased 2b. the amount of time is decreased 3a. 60 because they add up to 90 3b. 75 because they add up to 90 4. That must mean that this is the greatest angle they can achieve, achieving a 45 degree angle would probably be close to impossible. 5. Probably because his tride was long and he could jump at a higher angle and with more power than everybody else. 6a. at point x his acceleration is -9.8 m/s^2 downward because that is his highest point. 6b. The direction is 0 because the horizontal acceleration at this point is 0. 7a. -29.4 m/s 7b. 5 m/s 7c. 15 m (work for 7) 8. A 45 degree angle always allows the ball to travel the furthest when there is no air resistance 9. The highest angle measure would be the one that produces the most height. (90 degrees). 10a. The ball is accelerating east. 10b. the object is in the air for 4.5 seconds 10c. the distance is 90.3 meters. (work for 10)

Physics plus #1 and 2



What do you think now?

Some angles have corolations to eachother while others dont. Two angles that add up to 90 will land in the same spot if everything else is the same. Also, to achieve the highest hight, a 90 degree and is best. A 45 degree and produces the farthest trajectory. a greater launch speed could change its range because when something is moving fast, it will cover a larger distance.

=Section 6=

What do you think?

I would tell them to try and get as low as possible and exert alot of force on the ground so you can spring up and reach the highest height you can. It you get lower, you can probably have more force to apply downward which in turn wold spring you upwards.

Physics talk

The force of a student pushing against the wall is equal and opposite to the force that the wall pushes back on the student. This is newtons third law and it happens all around us. Even when we walk because we are pushing backward with out foot but we move forward. When two forces are pushing against each other, (like the demonstration with the scales) the force is always the same for both. "You cannot touch someone without someone touching you back." - this is a good way to remember that there are always two forces whenever you come into contact with something. A diagram that shows all different types of forces is known as a free-body diagram. There are forces everywhere with a push or a pull. Even when we stand, the only thing that keeps us from going through the floor is that the floor is pushing us back and it bends a little but not noticable.

Checking up

1. Newtons third law states that forces come in pairs and for every force applied there is an equal and opposite reaction that pushes back. 2. The equal and opposite reaction is that object itself pulling upward. 3. A free body diagram illustrates all the forces that apply to a certain abject.

PTG

1. Yes this happens because for every action there is an equal and opposite reaction that is made. 2. No, obviously chairs are not intelligent, this happens because it is a law of motion, and there are springs that cause the chair to safley balance the weight you have while pushing up back on you. If this process did not work, then you would fall because the chair would not hold your weight. 3. A scale has somekind of spring or platform that calculates how much force you are pulling on it. According to the amount of force you are putting, that is how far along the numbers the needle moves. 4. The force for these two things is the same because of newtons first law. Bats sometimes break because they cannot equal out the force the ball alys on them so they cannot spring it back and therefor they snap. 5. The force excerted by the players is the same, but it is the size of the players as well as other factors that determines which one goes down. 6. The player excerts a force on the boards as he hits it, but the boards exert that same force back on the player according to Newtons third law. 7. Baseball players use gloves to catch baseballs because the force that the ball exerts would be felt by the glove, and not your hand. The glove would then be the one that exerts the force back on the ball and not your hand which would hurt. For example if the ball exerts a force of 8 N on the glove, the glove exerts 8 N on the ball. 8a. As the tennis player makes that great shot, the ball hits the racquet with a large amount of force. The reason that the ball does not go straight through the racquet is because the racquet exerts this force right back and the ball. That among other things is what helped the ball repel of the players racquet and win him the point. 8b. The floor also exerts forces on things because if a basketball bounces on the floor, the floor pushes back with an equal and opposite force. The floor is indeed bending a little but it is so microscopic that we cannot see it.

What do you think now?

When you push with your feet, you are applying force on the floor, but what you may not know is that the floor is applying an equal and opposite reaction up through your feet, and another force that you apply is your own weight which is directed downwards throught the floor.

=Section 7=

What do you see?

There is a guy who is iceskating and he finds it easy to pull his shoe, however at the beach it is hard for him to push the boot on the sand.

What do you think?

Some sports require special shoes because there are certain parts of sports that require you to do a certain thing such as skate of run and there are different terrains for each sport. Different features like spikes on cleats would be useful in sports such as baseball and football because they allow you to have a better grip on the field. In sports like hockey, the "shoe" is a skate that has a blade which is specialized in cutting smoothly through the ice.

Physics Talk

The second force in the investigation was the friction between the shoe, and the floor The pulling force was the same as the frictional force because they are both on the x axis. If something does not move in vertical velocity the y acceleration is always 0. The coeficiant of sliding friction is represented as mu. mu=F/N Mu does not have any units attached to it and most of the time it is expressed in decimal form.

Checking up

1. Because these forces are on the x- axis and the force of friction is opposite to the pulling force so they have to be equal to eachocher. 2. The coeficciant of friction has no unit because when you divide two forces the units go away. 3. The force of friction divided by the normal force is Mu or the coefficient of friction.

Physics to go.

1. If you are playing tennis and it is raining, you might want to put on shoes that have better friction with the ground because it you do not and you go to stop then you will slide out. 2. A sport where the frictional force should be as small as possible is snowboarding or surfing because if there is not alot of friction between the board and the other surface, then it could glide farther, longer, and faster. 3. No you cannot be sure because a different courtcan be differently waxed and therefor may either be more slippery or less slipperyt so knowing how the floor is kept would help determine this. 4. This is because different surfaces have a different coefficient of friction between the surface and the shoe. For example clay may have less friction than concrete. 5. mu=F/n .03=x/600 N x=18 N for the skiier to remain at constant speed. 6a. w=mg w=(1000)(9.8). w=9800 N 6b. mu=f/N; .55=f/9800. f=5390 N 6c. F=MA. -5390=1000a. a= -5.39 (m/s)^2 6d. Vf=Vi=at. 0=Vi +(-5.39)(6) ; Vi = 32.34 6e. He was not driving 29 m/s but rather 32 m/s. 7. I think that these types of resistances change, for example, when you are walking with your feet in the water, it is easy to move slow, but once you start to move faster it is harder for your legs to move. This is because the water resistance increases. 8. Yes, this sets the limit for how fast you can start. it would not matter how strong your leg muscles are because there is a max force. 10. Friction is important in running because there are certain surfaces which call for alot of a little friction. For example, in football, you do not want to be slipping when you change direction so there are cleats that have a large amount of friction between the ground so you will not slip. The same thing happens in soccer as well. 11. At the national snowboarding championships, friction plays a huge role as to how the competitor's run down the mountain will turn out. The boarder with the least amount of friction between the snow and the board will likely go faster because there is not alot of friction there to slow it down. If a board has bumps on the bottom of it, that will create more friction and may slow the rider down and cause him to loose the race.

Physics Plus



Lab X 7

Table 1-

Tension trials (N)- 3.3, 3.2, 3.4 Ff(N)=3.3 Total Wight (N)= 11.8 mu= .28 class average=.325 % difference= 13.8

Table 2- Calculations N-w=0 N-1.6=0 N=1.6....... .28=f/1.6.... f=.46N .46=.17a....a=2.7 m/s^2 vf^2=Vi^2+2ad 0=Vi^2+ 2(-2.7)(4.8) sqrroot of -25.92=5.09... ect. Vf=Vi+at 0=5.09-2.7t -5.09+-2.7t t= 1.88 % error calculations done by calculated time-measured time/calculated time X 100

questions-

1. In part one, the coefficiant of friction shows how rough or smooth the surface the black was on was. (it puts a number on it) 2. Our mu is close to what the class got but not exact. The results should obviously differ due to the many random errors that could have accured but they should be close because every block weighs relitivaly the same amount and they are being dragged on the same surface. 3. my percent error was a bit on the high side. But this is understandable because i may not have clicked the timer at exactly the right times. 4. Yes it apply to the real world because there is friction all around us and especially in sports where someone can calculate things like the coefficient of friction on certain surfaces. 5. source 1- stopping and starting the stop watch at wrong times will throw off the measured times. Source 2- not starting the slide directly at 0 meters would throw off the measured distance calculation. Source 3- if the block did not slide the whole time and bounced around a little bit that could throw things off as well.

What do you think now? Some sport require a special shoe because it gives them better traction on different types of surfices. Also, the friction on different surfaces varries so the type of shoe you need (whether it needs spikes or not) is based on the surface you are playing on. Different features are useful for pretty much the same reason. For example, the coefficiant of friction can be small on a slippery basketball surface so the shoe would have to have feature that prevent it from sliding out.

=Section 8=

What do you think?

This is because it is not solely about your pole, but more of how fast you are running and when you pole vault. So therefore, you may not be able to clear a 12 m high bar because it would be impossible to go the speed that you are needed to be at. The factors that limi the height the pole vaulter can go are his horizontal speed and acceleration.

Investigate

a. Our technique involved bending the ruler with the penny on it while the other end of the ruler is held down. We will realese and the penny will fly into the air. b. Factors: how much deflection it has, position of the penny, flexibility of the ruler, how much it sticks out, and how high above the ground the ruler is.

1a. At the end of our experiment, we will be able to conclude if and hoe the defflection effects the height that the penny launches. 1b. We will record the height of each trial and the deflection of the ruler for each try. 1c. Tools: Ruler, Penny, meter stick, tape. 1d. We will analyze our data by putting it into a table and seeing if there is any relation between the amount of deflection and the height the penny achieves



Conclusion: Yes, the deflection of the ruler does have an affect on how high the penny goes.

Physics Talk

When a ball is thrown upward. It initially has alot of speed traveling up, but gravitational force is what slows the ball down and will eventually cause it to fall back down. This proves that forces often change from one to another without us even knowing it. Kinetic Energy is energy associated with motion. Gravitational Potential Energy is energy that is associated with position relative to the ground. Potential Energy=total energy When something is acted on that is neither gravitational or kenetic (usually in the form of pushing or stopping) it is called Work. When work is done, the energy of that object changes. Another form of Energy is known as Elastic Potential Energy. this is pretty self explanatory because it is the energy associated with a spring. When a pole vaulter goes up into the air. He is using every type of energy from work to Kinetic with gravitational and elastic in between. Equations: W= F x d; EPE=1/2kx^2; GPE= mgh; KE=1/2mv^2

Checking up

1. A force would help change the energy of the object 2. The penny gets its energy from both work (us pushing down on the ruler), elastic, and kenetic energy 3. The pole vaulter gets this energy from work and kinetic energy which then turns into elastic energy 4. These things are measured in a unit called Joules.

PTG

1. The person does work, then there is kenetic anergy which turns into gravitational potential energy and finally work is again done by the ground when the ball hits it. 2. The player hits the ball using work, the ball is then airborn and experiences both Kinetic and Gravitational energy, then the ground does work by stopping the ball. 3. KE=GPE 1/2mv^2=mgh 1/212^2=(9.8)x 72/9.8x h=7.34 m

4. because there are other factors that are involved such as the speed. 5. The pole increases in temperature because the vaulter is doing work on it when he bends it, so theoretically is he does too much work on it the pole could easily snap. 6. KE= GPE (masses cancell) 1/2 V^2=9.8(4.55) V=9.44 m/s 7. KE=GPE 1/2mv^2=mgh 1/2v^2=9.8 x 6.14 v=11 m/s. Sergei is faster 8a. GPE=KE mgh=1/2mv^2 9.8 x 100=1/2v^2 velocity= 44.2 m/s 8b. no you dont need to know the masses because they cancel. 9a. W=EPE F x d=1/2kx^2 W=1/2(1500)).25)^2 W=46.8 9b. EPE = KE 1/2 kx^2=1/2mv^2 1/2(1500)(.25)^2=1/2(.1)v^2 v=30.6 m/s 10. EPE = w 1/2kx^2=F x d 1/2 (315)(.3)^2= F x d 14.2= W 10b. 14.2=F x .3. F=47.3 N 11. GPE=EPE mgh=1/2kx^2 .04(9.8)=1/2(18)x^2 x=.21

12. N=kg x m/s^2. so a Newton= kg x m/s^2 12b. (kg)(m/s^2) so 1kg x 1m/s^2= 1J 12c. KE=1/2mv^2.... (kg)(m/s^2)...J=kg x m/s^2 12d. EPE+ 1/2 kx ^2.. (kg)(m/s^2)/m(m^2....J=kg x m/s^2

13. EPE to GPE to KE 14. W to KE to GPE 15. The ball hits the bat as work is being done by the batter. Sudennly the ball is juiced up with Kinetic energy as it flys up to gain its gRavitational potential energy. as the ball lands in the dirt, it has work being done to it once again. 16. In the play we are going to use, the player does work on the ball by kicking it. it flys into the air and has Kinetic, and then it has gravitational. as it lands in the goal, the ground does work.

What do you think now?

because it is the speed that matters and not the pole. And there is a limit to how fast people can run. Limits- the speed and their height. mass doesnt matter because it cancels anyway

= Section 9 =

What do you think?

I believe that some athletes have ways of "bending that law" so that they can stay in the air longer if they need to.

Investigate

2. 20 frames 3. that was a total of 2/3 of a second. 4. In the middle. he was spinning in the air but vertically he was not going up or down so yes, but it is not that he is not moving, but the differances in height are so small that it looks like he is hovering. 2a. 31 frames 3a. this represents about 1 second 4a. No he did not appear to hang in the middle

1. First you bend your knees, then you straighten them out, and then you are airborne. Initially we are doing WORK by bending and unbending our knees. As you are off the floor you end up with GPE. 2a. At the end of the experiment you will be able to know how much force you have on the ground when you jump up 2b. We will record the height of the jump, the force we have when we are just standing, the force of our push off, and the force of our landing as well as our weight and max height. 2c. Meter stick scale and platform 2d. We will use graphs and platforms to look at how the force differs from our weight and throughout the whole jump.

5. W= GPE F x d =mgh F x .1= (58.96)(9.8)(.29) F=1675

My calculations were a bit off. My actual run was lower than what i had calculated but this is parciallly because it is almost impossible to duplicate your jump. Error- [1675-1263.47]/ 1263.47 x 100 = 32.5 %

Physics Talk

In the investigate, we experienced a teansformation of energy through the motion of a jump. When we get ready for the jump (knees bent) we are loaded with Elastic potential energy. This is the same as how it would be in a spring before it is released. At some points, such as our launch position we have both Kinetic and Elastic energy but they both add up to the same amount of the ready position. At each position the amount of energy needs to be the same for all three or however many there are. In most systems there is a conservation of energy simular to this. for example when you are on a trampoline you first have GPE then you have a combination of KE and GPE and at the lowest point of the trampoline you have Elastic energy ready to spring you up:

Checking up:

1. Here the energy comes from the Kinetic energy as well as the Elastic energy when you bend your knees and act as a spring. 2. The student will have Elastic Energy but then will experience some Kinetic energy because he begins to move upward. At the peak of the jump, he has Gravitational Potential Energy. 3. Light chemical and sound energy.

PTG

1. W = GPE W= mgh W= 50(9.8) W=490 J 2. The energy involved goes as followed: Work is done by the players pushing the sled, there is Kinetic energy when they are in the sled, and finally the sled stopps because of the work by its brakes on the ice. 3. We could set up an experiment simular to what we did on the board with the video. Place a marker after each tick and see if the player is really hovering or not. 4. I think the burden of proof should be on the person who makes the claim because if you make a claim then you should be able to back it up. 5. You can increase your jump by bending your knees more, and losing weight. 6a. W=F x d W= 1 J 6b. 1 x 10 = 10 J 6c. 10 N x 1m= 10 J 6d. .1N x 100m= 10 J 6e. 100 N x .1 m= 10 J 7. Work equalls GPE so there is no differece 7a. 1J 7b. 10 J 7c. 10 J 7d. 10 J 7e. 10 J 8. KE=GPE 8a. 1 J 8b. 10 J 8c. 10 J 8d. 10 J 8e. 10 J 9. W= F x d W= 50 x 43 W = 2150J 10. KE = 1/2mv^2 KE= 1/2(62)(8.2)^2 KE=2084.4 J 11. a = F/m a= 6 m/s^2 11b. W= F x d W= 30 x 18.75 W=563 J 12a. W = F x d 40000= 3200 x d d=12.5 12b. a = F/m a=2.7 13. KE=W 1/2mv^2=W W=120 J 14. W=KE F x d=1/2mv^2 417d=1/2(64)(15)^2 d=17 m

15.

16 . 17. 18. The ball is kicked. The players foot does work as the ball is propelled into the air because of Kineic energy which at the top of its flight turns into Gravitational energy, and then is stopped by the ground doing work when it lands.

Physics Plus

1a. KE = GPE 1/2mv^2=mgh 1/2v^2=(9.8)(50) 1/2v^2=(9.8)(30) v=19.8 m/s 1b. In this senario it is adventageous because the masses cancel so you do not need to know them 2. EPE = KE 1/2kx^2=1/2mv^2 1/2(60)(.4)^2=1/2 (.3)v^2 v=5.66 m/s 3. GPE+Work (initial)= KE +GPE + Work (final) mgh+ F x d= 1/2mv^2+mgh+F x d (200)(9.8)(25)+200000=1/2(200)(40)^2+20(9.8)(x)+50000 249000=160000+1960h+50000 89000=1960h +50000 39000=1960h h=19.89m

What do you think now?

No, i do not think that they defy gravity because they are simply transfering their energy from one type to another. For example, when a figure skater jumps, and appears to hover for a bit at the top of his jump, this is only because he has reached max height, and there is no longer any KE for that second. He is transfering to Gravitational Energy and soon will be on his way down.