CH2_depolj

=Chapter 2= toc

Section 1
Physics and Sports: A science magazine explored why snowboarders are making record speeds and calculating how scientifically they are able to do back flips. http://extremesportsphysics.blogspot.com/

What do you see?

The kid who is running kicks the ball a lot farther than the kid who is standing still.

What do you think? How do figure skaters keep moving across the ice at high speeds for a long time while seeming to expend no effort? Why does the soccer ball keep moving after it is kicked? As the figure skater starts skating, she starts building up momentum which keeps them moving. It will be harder to stop. The heavier the object/ person is the faster and the longer they are going to keep up speed. The harder the ball is kicked the father the ball is going to travel.

Investigate:

hypothesis: The steeper the track is the fast the ball is going to move because it gains more momentum and allows it to travel farther.

1. E) It is the same if both sides of the track are equal. it is 4.04m starting him at 4.04m  2. a) He will go farther than he initally started b. The steeper the incline the farther it will travel 3. a. he ended up being at the same place as he started. We thought that it would have ended up higher than it actually went. b) the place where he started is where he ended up. 4.a) its not going to pick up as much speed. b) The person reached the same height as where he started. 5. a) No because he falls off the side if there is zero slope. b) He is going to roll off the track and continue until he loses all momentum. c) If you point the ends up slightly, it will help keep the guy on the track. d) we were correct. 6. a) His speed decreases. b) its going to travel until it falls off. c) If the slope is equal it will be equal. d) when they loose all momentum.

read and summarize 134-138

Galileo Galilei was an Italian physicist, mathematician astronomer, and philosopher. Galileo is called the father of modern science. Inertia is the naturel tendency of an object to remain at rest or to remain moving with constant speed in a straight line. Rolled a ball on a ramp and it kept rolling without friction. It will always try to reach its intital height. Force is a push or a pull. 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 a constant speed in a straight -line path. Newton said that the mass of an object is its measure of inertia. Interia is a property of matter that measures the resistance to change in a object is motion. MASS( kilograms) is how we measure interia. weight: how much gravity pulls on a mass. velocity is speed with direction. acceleration is the rate of change of your speed. Frame of reference: perspective.

Checking up questions: 1. What is Inertia? Inertia is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. 2.Describe Newtons 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. 3. What needs to act on an object to stop it from moving at a constant speed. An outside force needs to act on the object. 4.In the real world, a rolling ball does not roll forever. What stops the motion of the ball? it looses momentum or another force acts upon it. FRICTION 5. Given two different - size masses moving at the same speed, which mass will have the greater inertia? The larger the object the faster it is going to move. Greater mass. 6. You throw a ball in a moving train. Why is it important to establish a frame of reference when describing the speed of the ball. Speed of ball relative to the ground, or train or yourself.

Physics to Go:

1a. the ball will roll forever unless an unbalanced force comes into contact

1b. Newton's first law of motion: an object already in motion remains in motion with constant speed in a straight-line path

2. It will reach a vertical height of 20 cm again.

3. I don't think that it would be possible to have an object move in a straight line forever because there are obstacles EVERYWHERE. There are changes in surface and also, air in general can be the force that stops an object in motion. Everything has a little bit of friction.

4. The puck moves or "glides" across the ice. It keeps moving in a straight line until it hits the stick (the unbalanced force stopping the motion). Players will purposely have the puck hit the wall so it will reflect and go into a different straight motion.

5. The nearby person sees it go by at 7 m/s (2.5+4.5)

6. The javelin relative to the ground is 14.5 m/s (10.3+4.2)

7a. relative to the ground: 8 m/s forward (5.6+2.4)

7b. relative to the tracks when pushed towards the rear: 3.2 m/s forward (5.6-2.4)

7c. velocity relative to the ground when you and your friend push the cart perpendicular to the aisle as the train moves forward? 6.1 m/s at 67 degrees from cars direction (Pythagorean theorem: v = square rt of 5.6^2 + 2.4^2) (inverse sohcahtoa)

8. The arrow left the bow at 67 m/s

9a. sin45 x d = 15 cm; d= 21.2 cm

9b. sin20 x d = 15 cm; d= 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: the puck if not touched will stay at rest and will continue to do so unless a force is acted upon it. When it is hit, it will stay in a straight line motion until it comes in contact with another force (stick).

-soccer: the ball if not touched will stay still at rest. When it is kicked, it will go in a straight line constantly until it is stopped by the goal or another player.

-crochet: the ball if not hit will remain at rest. It will move in a straight motion forever until it is stopped by a bat or a post

10b. Sportscaster style:

- What do you think now?

The figure skater glides because without an outside force she will keep gliding. Friction will cause her to eventually slow her down.- The momentum build up causes them to glide effortlessly across the ice. The heaver and harder the skater pushes, the longer they are going to be able to glide. - The force that is applied to the ball causes the ball to travel for a long period of time until friction acts upon it to cause it to stop.

- It is the amount of friction that is applied to the object. That is what causes the ball or skater to go for a long period of time.

Inquireing further:

Curling shows Newtons first Law if motion because it exhibits friction. In curling the object that was thrown travels in a straight line motion until it is interrupted by another force or object. This analogy is not a perfect indication of friction because there is a little friction on the ice which slows the object being thrown down. source: physics of curling []

Find and record three sports where there is motion with constant speed, and record when this motion takes place in that sport - bowling: the lack of friction down the path causes the bowling ball after it is thrown to have a constant speed - soccer: when a player kicks a ball for a penalty kick it has a constant speed until it is stopped by another player. - curling: after the object is tossed on the ice it has a constant speed until it is interrupted by another object.

Section 2
What do you see? There is a boy who is walking slowly and his foot steps are close together. There is also a boy that is running with flower. His foot steps are spread farther apart.

What do you think? In your own words, explain the meaning of 100 mi/h and 45 m/s. These speeds come from the pitchers throw, from the moment i the ball leaves his hands to when it gets to home plate.

Physics talk: Acceleration is a change in the velocity of an object over time. Average speed is the distance traveled divided by the time taken to travel that distance. Rate at the distance is traveled. Average speed= change in d/change in t. Instantaneous speed is the speed measured during an instant: the speed as the time interval approaches, but does not become zero. when the signs of v and a are the same, you are increasing speed. When the signs of v and are opposites the speed is decreasing. Checking up: 1. Describe the pattern of dots on a ticker tape for each of the following situations: a) constant speed: there are equal spacings (distance) between each dot. b) positive acceleration: The spaces start out close together and then gradually become larger. C) negative acceleration: the spaces start out far apart and then become closer.

2. An athlete runs 400 m in 50 s. What is the runner's average speed? average speed = distance/ time. = 400/50 = 8s

3. What is the difference between instantaneous speed and average speed? Average speed is the distance traveled divided by the time taken to travel that distance. Instantaneous speed is the speed measured during an instant: the speed as the time interval approaches, but does not become zero.

4. A vehicle accelerates from 0 km/h to 100 km/h in 10 s. What is the average acceleration? acceleration: change in speed/ change in time. =100/10 = 10s .0028h vf= vi+ a

Physics to go: 1. In your own words compare average speed and instantaneous speed. Average speed is the average of all the different speeds and instantaneous speed is one speed at any given moment. 2. Calculate the average speed in each of the following situations: a) a horse runs 1 km in 15s. 1/15= 15s b) a skier travels 84m in 6s. 84/6=14s c) you walk 9.6 in 2 h. 9.6/2= 4.8s d) A car travels 400 km in 4.5. 400/4.5=88.88s In which of the following cases is acceleration occurring? If so is its positive or negative? a) a runner falls down- negative acceleration b) a runner takes off from a starting block. Positive acceleration c) you walk down a straight hall at a steady speed. no acceleration, d) a soccer ball is caught by the goalie. negative acceleration. e) a bowling ball rolls along the gutter at constant speed. no acceleration  f) a parachutist falls at a constant speed. negative accelertion. 4. a) graph A is constatnly increasing.  b) graph B is moving at a constant speed. c) graphs A and C have the biggest change from the first speed to the second.  d) Graph C is first increased and then later decreased. e)

14.  a) With a constant motion the tape will all be the same length.   b) The spaces between the dots will be farther apart when its a fast constant motion. c) The spaces between the dots will be smaller when going at a slower constant motion  d) The dots will start out closer together and then spread out as time goes on ( positive acceleration) e) The dots will start out farther and then become closer. (negative acceleration)

Physics Plus: rebounding( any object) || Rebounding is when you change direction. Even if speeds are small accelerations can be huge if the bounce time are tiny. - even if the speeds are small the acceleration can be huge if the bounce times are tiny. 3) 5 b) 5 c) 5 What do you think now?
 * velocity || accel || example ||
 * small || small || turtle ||
 * big || big || airplane, racecars ||
 * small || big || rabbit, deer, dog
 * big || small || truck ||

100 mi/h and 45 m/s both measure velocity and distance in relation to time. They are both examples of average speeds and instantaneous speeds because Velocity is found by dividing the distance traveled by the time.

Section 3:
What do you see? One person who is pushing a ball at different speeds. The first he is walking, secondly he is running and the third looks like he are sprinting. What do you think? Force is something that acts upon something else to make it do something. Force is a push or a pull. Since a bowling ball and a tennis ball have different masses if you apply the same force on both there will be different results.The tennis ball will move further because there is less mass.

Investigate: Group wiki

Physics Talk: - Newton's 2nd law: acceleration= force over mass or a= F/m - a= m/s^2, m=kg, f= N - when there's acceleration, there must be an unbalanced force - second law: accelerations are caused by unbalanced forces, doesn't matter what kind of force or how it starts - something with large mass moved by a force will move less than something with a smaller mass moved by the same force - in the case of the force bending the ruler, this force is due to gravity - the force gravity causes is weight - weight: the force of gravity acting on an object, and it depends on the mass of the object and the acceleration due to gravity. - w=mg - g is the acceleration due to gravity - when once force acts on an object, the object accelerates - when 2 forces act at the same time, the direction as well as the magnitude of the forces determine the motion of the object - if the forces are in the same direction, then the sum of the forces or net force will cause a larger acceleration than either force alone - if two forces are in opposite directions, then the net force could be zero and there would be zero acceleration - free-body diagram: diagram used to show the relative size and direction of all forces acting on an object - net force is directly proportional to acceleration Fnet= m*a - a big force causes a big acceleration, a small force causes a small acceleration - a big mass needs a big force to accelerate, a small mass needs a small force to accelerate - net force has no relationship to velocity - force and acceleration can't have different signs, they have to be the same direction

Checking Up Questions: 1. Newton's second law says that without an unbalanced force there will be no acceleration. 2. It will make the acceleration smaller because more force is needed to gain velocity. 3. If an object weighs 30 Newtons, it means that its mass times the force of gravity exerted on the object is 30. 4. If on a planet with higher acceleration, you would weigh less because the higher the acceleration, the lighter the mass is. Also, you would need less force to accelerate.

a.350N, b. 80 kg, c. 10 m/s^2, d. 80 kg, e. -15 m/s^2, f. -3000N 3. F = (m)(a) ; 42N = (.30kg)(a); a = 140 (m/s)/s 4. F = (m)(a) ; F = (.040kg)(20m/s^2) ; F = .8N 5a. Newton's first law of motion: a bowling ball had a larger mass than a baseball. Therefore it has more inertia. A greater force than a human would need to throw the bowling ball fast enough so it continues at fast speed. The baseball has less inertia but will travel in straight-line motion for longer and with greater force because it easier to for the force of our bodies to accelerate it. 5b. Newton's second law of motion: In the equation F=ma. Mass and acceleration are indirectly proportional. So, a baseball with less mass will have a greater acceleration than a bowling ball with a larger mass. Therefore, it is going faster when it hits your hand, so it will hurt. The bowling ball will go slower (less of an acceleration). 9. When you throw a ball, the force of your hand is acting upon the ball until an unbalanced force comes in contact with it.

10. 50N + 40N = 90N 11. 4 adults x 200N each = 800N 12. F=am; 125N =a(.7kg); 179 m/s^2 15. F=mg ; F=(12.8kg)(9.8m/s^2) F= 125 N 18. Sports announcer: A tennis ball of .057kg was just served at and accelerates at 430 m/s^2. That great serve was made with the server's swinging and body force of 24.51N.

active physics plus: 1. 125N +125N= 250 N 2. 40-70= 30 south b)70-40-40= -10N c) south because it has the greatest force.

ptg: 13. 120^2 + 50^2= 16900= 130 -tan 120/50= 38.6 North 14. 4000^2+5000^2= 6403 -tan 4000/5000=38.6 east 16. 30^2 + 40^2 = 2500 = 50 -tan 30/40=36.8N 17. 30^2 + 20^2=1300 = 36.05 -tan 20/30= 33.69

What do you think now? A force is a push or pull which acts on any given object. Because mass varies inversely with acceleration, the greater the mass the slower the acceleration will be. Therefore the same amount of mass goes goes a longer way with the tennis ball rather than the bowling ball.

**Section 4** What do you see? There is a girl standing on a ladder throwing one apple across and one down. There is a boy timing both. What do you think? The speed, strength, force, angle weight and height in which the object is thrown determines how far the object will travel before landing. Physics talk: Projectile: an object traveling through the air or other medium(acted on only by gravity). Trajectory: path The X and Y component of any vectors are independent. Vertical velocity affects vertiacal distances (y) Hoizantal velocity affects horizantal distances (x) the time it takes projectile to hit the ground (hang time) is the same as the time it takes to drop (level) acceleration due to gravity is - 9.8 ertical velocity changes by -10s every second horizantal velocity does not change ever mass is irrelevant Vy =0 (maximum height) launches hoizantaly results in the same path as the second half of a ball being thrown at an a ngle. Checking up: 1. Yes the same height acceleration is working on both 2. no it increases about 10 per second. 3. 0 the acceleration is -9.8

PTG: 4. The bullets are going a lot faster. They would believe that the one being shot would reach the ground faster than the one that was just dropped. 6. It has no effect on it because the chair is moving the same pace as the ball.

Video http://www.youtube.com/watch?v=_SZhLz9VTio This video shows the angle trajectory of a basket ball being thrown into the hoop. When the ball is in the air and reaches the net is where the horizontal velocity.

PTG: 7. A and B are going to hit the ground at the same time because gravity as acting on both of them equally causing them to do so. 8. 3.6 m/s @ 34 degrees 9a. 11.98 m/s 9b. 23.96 m 10a. 8.5 m/s 10b. 4.25 m 11. In baseball when the ball is pitched and then hit into the outfield. What do you think now? What determines how far an object thrown into the air travels before landing? launch velocity What do you think determines how far an object travels after it is thrown? initial height and the initial speed - When the initial height is changed (increased or decreased) and the launch velocity is changed (increased or decreased) it determines how far the object is going to go while it is in the air.

Chapter 5:
What do you see? I see a ball being kicked up, and then falling down, bouncing off a boy's head and going up & then down again. What do you think? 1. smaller angles have long ranges velocities and are up for a shorter amount of time larger angles have smaller rangers and are up for longer amount of time 2. The greater the speed, the faster (covering more distance) the object will travel, so the range will be longer. Physics Talk  summary: Projectiles can have two motions that act at the same time and do not affect one another. One of the motions is constant speed along a straight line, corresponding to the amount of launch speed and its direction. The second motion is downward acceleration at 9.8 m/s^2 caused by earth's gravitational force, which takes effect upon launch. Trajectories of projectiles can be modeled using a computer or graphing calculator; which allow you to manipulate variables such as launch angle, speed, height, and range to enhance your ability to simulate, explore, and understand projectile motion. The path of all trajectories are parabolas. Small angles have greater horizontal velocities but are in the air a short time. Large angles have smaller horizontal velocities but are in the air a long time.

 Checking up:  1. What are the two types on motion that help you understand the trajectory of a projectile? One of the motions is constant speed along a straight line, corresponding to the amount of launch speed and its direction. The second motion is downward acceleration at 9.8 m/s^2 caused by earth's gravitational force, which takes effect upon launch.  2. What is the fundamental requirement a scientist must meet when proposing a model of some natural phenomenon? The model must math reality in nature.  3. For projectiles launched at various angles, summarize how the heigh and range of projectiles vary as the angle of launch is increased from 10 to 80. When it is increased from 10 to 80 the height is going to increase. The range will also increase, but at both 10 and 80 they have the same range.

Ptg: 1- 6 1. The 45 degree angle produces the greatest range. 2. smaller angles are in the air for a shorter amount of time and larger angles spend more time in the air. 3. 30 degrees= 60 degrees 15 degrees=30 degrees 4. Human error. 5. Because Carl Lewis is a fast runner he is able to project himself when attempting the long jump as well. 6) a) a=-g=-9.8 m/s^2 down b) Vmax: Vix only because Vy= 0 at max height 7) a) V= Vi +at -9.8 x 3 = 29.4 m/s  Vertical speed final: 29.4 m/s 7) b) horizontal speed after 1 second: 5m/s 5:VIT vi:5.0 7) c) 15 m from the cliff d:vit d:15cm 8) 45 degrees creates the longest range 9) the largest angle 10) a) direction of acceleration: down 10) b) -100 : .5 x -9.8 x t^2 t = 4.5 seconds to reach the ground 10) c) d : vit+1/2 at^2 d: 20 (4.5) d: 90 meters from the base of the cliff. Ptg 1.

2.

What do you think now? A 45 degree angle gives the longest range. Anything bigger gives you more time in the air but a shorter range. Any two complementary angles (15&75; 20&70) give you the same range. a greater launch speed of a projectile might change the range when the launch angle is the same because if it is launched faster it is going to go farther.

Section 6: What do you see? There is a boy sitting on an office chair with his legs bent up, pushing against a wall. The second part of the picture shows the boy pushing off the wall and gliding backwards.

What do you think?

The high-jump record is 2.45 m (about 8 ft) for men and 2.09 m

(about 6 ft) for women.

**Pretend that you have just met somebody who has never jumped**
 * before. What instructions could you provide to get the person to **
 * jump up (that is, which way do you apply the force when you **
 * push with your feet)? **
 * If I had to instruct someone to jump first I would tell them to keep their feet flat and bend their knees. Then they would have to push off their feet in order to spring upward. **
 * Physics talk**
 * - newton's third law: for every applied force, there is an equal and opposite force. The two forces always act on different object, **
 * - 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...this is an inescapable fact- it happens every time, forces always come in pairs **
 * - ex: if you push on hte wall, the wall pushes on you with the same force **
 * - free body diagram- a diagram that shows the forces acting on an object, a diagram used to show the relative strength and direction of all the forces acting on an object in a given situation **
 * - each force is represented by an arrow, the direction is in the direction of the force, the size of the arrow is the strength of the force **
 * - each arrow is labeled to tell the type of the force **
 * - center of mass- point at which all the mass of an object is considered to be concentrated **
 * - the weight of the object can be represented from that point **
 * - other forces can be represented by arrows emerging from the contact point **
 * - the equal and opposite reaction happens instantaneously with the action that causes it, no delay **


 * Checking up questions**
 * 1. For every applied force, there is an equal and opposite force. The two forces always act on different objects. **
 * 2. You are the opposite force. **
 * 3. It shows the forces acting on an object. **


 * PTG**
 * 1. This is true because it puts an equal force on the persons hand just in the opposite direction. **
 * 2. The chair pushes up because there is a force from the ground pushing the chair itself up. The force applied to both is equal because the two objects are not moving. There are two types of deflection, on the chair because of the person and on the floor because of the chair. **
 * 3. A bathroom scale works by measuring the mass of your body and the gravity on your body creating weight . You have to set the scale to 0 every time so it calibrates correctly. **
 * 4. The forces on the bat and ball are in opposite directions but an equal amount of force. The ball is pushing towards the bat while the bat is pushing out on the ball. Bats sometimes break because of the velocity of the ball and the force used by the bat. The forces are equal and opposite but the bat is too weak so its going to break. **
 * 5. Because of the larger linebackers greater mass, he has a greater force meaning it is much easier for him to tackle a smaller linebacker . The small line back is going to have a larger acceleration. **
 * 6. When a hockey player hits the wall there is a normal force towards the wall and a gravitational force pulling down. **
 * 7. The greater the velocity of the ball, the greater force it has when it is stopped, this causes it to be harder to catch. Therefore wearing a glove protects one's hand from being hurt when catching a ball at such high speeds. **
 * 8a.**


 * What do you think now?**
 * The floor pushes up on you as you push on the floor. I would still instruct the person to bend their knees and put all your force on your feet. **
 * Whenever you exert a force an equal and opposite force is what happens in return. When you push on something a force pushes back. **

**Section 7:**

 * What do you see?**
 * There is a person on ice trying to pull a shoe but it wasnt going anywhere. **
 * What do you think?**
 * Different sports require different shoes because there isnt always an appropreite amount of friction. In soccer you have to wear cleates, so the spikes on the bottom hook into the ground and give you better leverage. Different features give players different advantages. **


 * Physics Talk: Friction: a force that resists relative motion between two bodies in contact. Pulling force you applied to the shoe is equal to the friction between the shoe and the surface its on. Normal force: the force acting perpendicularly or at right angles to a surface. Coefficient of sliding friction: a dimensionless quantity symbolized by the greek letter /u; its value depends on the properties of the tow surfaces in contact and is used to calculate the force of friction. It does not have any units because it is a force divided by a force. Usually is expressed in decimal form. Its valid only for the pair of surfaces in contact when the value is measured; any significant change in either surfaces may change the values. **
 * Checking up: **
 * 1. Why can you say that the force of friction is equal to the force reading on the spring scale when pulling an athletic show across a surface with constant speed? . the force of friction and the force on the spring scale are equal because the friction force and force applied when pulling was equal. They are equal but opposite. **
 * 2. Why does the cofficient of friction have no units? it has no units because it is force (newtons)/ force # 2 (newtons) **
 * 3. What determines the coefficient of friction? the force of friction is equal to the force required to slide the object this is the constant speed. **


 * PTG**


 * 1. In track a change in weather condition such as rain would cause the runner to want more friction so they would not slip while running. the runnner may want to wear different shoes that are a little heavier when running in the rain so they can gain traction. **
 * 2. Ice hockey is a sport that requires little friction because ice is a frictionless surface. In order to keep the friction down the players usually clean their skates before skating and play on freshly groomed ice rinks. **
 * 3. She is going to need to know what the floor of the court is made out of, however this is not true because all surfaces have a different amount of friction. **
 * 4. Tennis players need different shoes for different surfaces because some surfaces have more friction than other and therefore they would need different shoes to stay stable while playing. For example, because clay is a rough surface you dont need as much friction. **
 * 5. F= ma **
 * .03=x/600 **
 * 18N=f **
 * 6. **
 * µ=.55 **
 * t=6 s **
 * Vi= 29? **
 * a) w= 1000(9.8)= 9800N **
 * b) there is a normal force going upward, weight going downward and friction going to the left **
 * c) -f=ma **
 * -5390=1000a **
 * -5.39=a **
 * d) Vf=Vi+at **
 * 0=Vi(-5.3)(6) **
 * 32.34 **
 * e) no, he was lying. He was going more than 65 mph. **


 * 7. Air and water resistance remains constant, however the speed changes. No, when you are running and increasing your speed their is the same air resistance but the speed changes. It depends on the speed **
 * 8. u:f/n When there is a maximum force there is a limit put on how far something can be sent. There is a restriction on acceleration and the strength of your legs does not matter. You can reduce the friction by changing the surface to a less textured surface for example going from sand to ice. **
 * 9. An athlete shoe company would use our results by saying the shoes are not heavy and the lightest shoes around, there bottoms are thick so the players do not slide around on and have good traction while playing. **
 * 10. Friction is important to running because you need good traction to stay on the ground and not slip or fall. Cleats are used in football, soccer, and other sports because you need friction to keep the players feet on the turf and not slide. **
 * 11. Reporting from the PHHS track about the relay race tournament. The PHHS runners are all wearing special running shoes that they say are lighter which allows them to gain friction and run faster. **
 * Physics Plus:**




 * F=ma **
 * Wx-f=ma **
 * mgsin30-f=ma **
 * 1.5(9.8)sin30=0 **
 * 7.35=f **


 * f-ma **
 * N-Wy=ma **
 * N-mgcos30=ma **
 * N-1.5(9..8)cos30=ma **
 * N=12.7 **


 * Lab:**


 * Tension (N) || Ff (N) || Total Weight (N) || µ || Class Average µ || % Difference ||
 * 3.3, 3.3, 3.4 || 3.3 || 11.8 || .28 || .33 || 15.2 ||

**vf^2=Vi^2 + 2ad I used that equation to find all of the initial velocities**
 * Mass (g) || Mass (kg) || Measured Time (s) || Measured distance (m) || Ff (N) || Acceleration (m/s^2) || Calculated Vi(m/s) || Calculated Time (s) || % Error ||
 * 170 || .17 || 2.04 || 9.31 || 3.3 || -2.7 || 7.09 || 2.6 || 78 ||
 * 170 || .17 || 1.49 || 4.7 || 3.3 || -2.7 || 8.22 || 3.04 || 49 ||
 * 170 || .17 || 1.85 || 7.7 || 3.3 || -2.7 || 10.52 || 3.89 || 47 ||
 * Fx=ma **
 * -f=ma **
 * .28=f/1.6 **
 * f=.46 **
 * a=f/m **
 * .46/.17 **
 * a=2.7 **


 * 1. What does the coefficient of friction in Part I mean?**
 * It shows the friction and forces against each other between the block and the floor.**
 * 2. how does your µ compare to the µ of your classmates? Should your results be the same as everyone elses?**
 * My µ was very close to everyone else in the class. They should be close because we were all using the same materials.**
 * 3. How well did your times agree? Was your percent high or low? I had a 15.2 percent error so it is on the higher side.**
 * 4. Does the theroetical physics we are doing in class seem to apply to the real world? Yes they do. Detectives use this all the time to figure out car accidents and speeding violations.**
 * 5. Describe at least 3 sources of experimental error.**
 * The floor could not be exactly level. If the measuring tape was not perfectly straight it could have an effect. And if the timer did not start on time.**


 * What do you think now?**
 * Why do some sports require different shoes?**
 * All sports require different shoes so there is enough friction between the bottom of the show and the floor. In order obtain speed without slipping there needs to be friction. There is a normal force from the floor that is working on the shoe. The more sliding friction there is the harder it is going to be able to slide, which is why it is important when picking out shoes for particular sports. **


 * Reflecting: We have learned about the friction and how it effects different surfaces when playing sports. Friction is a key part in any game. **

**Section 8**
What factors (variables) do you think limit the height a pole vaulter has been able to attain? ** Acceleration, the weight of the jumper, friction between the pole and the floor. **
 * What do you see?**
 * There is someone pole vaulting. They are shown in different stages which helps us see that the person need to accelerate in order to reach maximum height. **
 * What do you think?**
 * If champion pole **vaulters can clear **a 6.0-m high bar with a**
 * //5.5-m// long pole, why **can’t they vault over **a 12.0-m high** bar
 * with a pole 11.0 m long? They do not have enough acceleration in order to get themselves over the 12 m high bar . **
 * Lab: **
 * A) record your technique for blasting the penny high in the air.**
 * Hold one end of the ruler and push down on either side. Push the side with the penny down without breaking the penny **
 * b) What factors about the ruler and how it is positioned determined the height the penny achieve.**
 * less the ruler sticks out **
 * greater deflection - force acting **
 * position of penny closer to the end. **
 * flexibility of the ruler **
 * How high above the ground the ruler is. **


 * Variable tested: Position of penny **
 * Methods and Materials: Apply the same pressure each time and move penny. **
 * Data: **
 * End: 70cm **
 * middle: 20 cm **
 * back: 2cm **
 * Conclusions: When the penny is at the end of the ruler the penny travels the farthest into the air. **


 * Physics Talk: **
 * Kinetic energy: energy associated with motion. Gravitational potential energy: the energy an object possesses because of its vertical position from earth. When a ball is thrown up into the air the force acting on it sends it upward but the gravitational force will pull it back down. Potential energy: energy associated with position. Law of conservation of energy: energy cannot be created or destroyed it can be transformed from one form to another but the total amount of energy remains constant. Work: the product of the displacement and the force in the direction of the displacement. Elastic potential energy: The energy of a spring due to its compression or stretch. **
 * Conservation of Energy: Total energy of a system remains constant although the TYPES of energy might change. Can be transferred from one type to another. The only way to increase or decrease energy is to do work. **
 * All the initial energy that you have + all the work done = the final energy + the work done by the system. **

PTG 8 1. You do work then it becomes kinetic then gravitationl to kenetic then work again. 2. work then kinetic the gravitational and kinetic.


 * 3. KE = GPE **
 * 1/2mv^2 = mgh **
 * 1/2(12)^2 = (9.8)h **
 * 7.3 m = h **


 * 4. What is really limiting the vaulter's height is his/her speed.The height a pole vaulter can reach is based on a few factors. His/her mass, their speed, the length of the pole, and the deflection ability of the pole. **
 * 5. The pole would increase temperature as the vaulter does work on the pole with first kinetic and then elastic energy. But at the pule straightens, it will decrease in temperature as the vaulter increases his/her gravitational potential energy **


 * 6. KE = GPE **
 * 1/2mv^2 = mgh **
 * 1/2v^2 = (9.8)(4.55) **
 * v = 9.44 m/s **


 * 7. KE = GPE **
 * 1/2mv^2 = mgh **
 * 1/2v^2 = (9.8)6.14 **
 * v=10.97 m/s **
 * Sergei's speed is higher than Emma's speed. **


 * 8a.) GPE = KE **
 * mgh = 1/2mv **
 * (9.8)(100) = 1/2v **
 * v = 1960 m/s **
 * 8b.) You don't need the mass of the rock because it cancels out **


 * 9.) Wpullback = EPEf **
 * W = 1/2kx^2 **
 * W = 1/2(1500)(.25)^2 **
 * W = 46.875 **
 * 9b.) EPE = KE **
 * 1/2kx^2 = 1/2mv^2 **
 * 1/2(1500)(.25)^2 =1/2(.1)v^2 **
 * v=30.6 m/s **


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


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


 * 12a. F (measured in N)= m(measured in kg) x a(measured in m/s^2) . Therefore 1N = 1kg x 1m/s^2 **
 * 12b. GPE=mgh ; (kg)(m/s^2) ; 1kg x 1 m/s^2 = J **
 * 12c. KE=1/2mv^2 ; 1/2(kg)(m/s)^2 ; 1kg x 1 m/s^2 = J **
 * 12d. EPE = 1/2kx^2 ; 1/2[(kg)(m/s^2)/m]m^2 cancels out to 1kg x 1 m/s^2 = J, the same way GPE = kx^2 does **
 * 13. EPE > KE > GPE > KE **


 * 14. W of v-ball player to KE of the ball on the way up to the GPE at its max height to the KE on the way down. **
 * 15. And the pitcher is putting work on the ball. The work transfers into kinetic energy of the ball moving towards the bater. And the bater puts work on the ball. The energy of the bater transfers to kinetic energy on the ball traveling out. The ball reaches max height and has gravitational potential energy and then quickly converts back into kinetic energy. The ground now puts work on the ball and it stops. **
 * 16. When trying to pole vault the KE that you have from your running start is all converted into your upward force so you can get high. **

What do you think now?

If champion pole vaulters can clear a 6.0-m high bar with a 5.5-m long pole, why can’t they vault over a 12.0-m high bar with a pole 11.0 m long?
 * They dont have enough speed in order to make it over the bar. Its the speed that matters not the length of the pole. The more velocity the more kinetic energy which allows you to get over the bar **

What factors (variables) do you think limit the height a pole vaulter has been able to attain? ** The amount of speed they can run at and their height. **

Section 9
What do you see? Someone is jumping and spinning while having a timer in the air.

What do you think? do atlethes defy the pull of gravity? Gravity is theroum not a law and it depends on how they get themselves in the air. Yes, they do because the pull of gravity would have pulled them down.

investigate: skater- 20 frames. 2/3 of a second in the air. she hangs a little in the middle of the jump. basketball player- 31 frames 31/30 of a second. (about one second)

W=GPE fxd= mgh f (.08) =49(9.8).26 f=1560.65N



physics talk: Conservation of Energy


 * The ready position has the maximum energy potential. The energy of all three positions has to be equal. **
 * All energies can be measured and calculated. When jumping you go through three positions. From the ready to the launch position gravitational Energy and Kinetic energy increases. **


 * Checking Up **
 * 1. The jumper can move from the ready position to the launch position from the contractions in the leg muscles- EPE **
 * 2. in Launch position the student has both GPE and KE. Peak of jump - GPE. **
 * 3. three other types of energy: light energy, chemical energy, sound energy **


 * PTG: **
 * 1. W=GPE **
 * W=mgh **
 * W= 50(9.8)1 **
 * W=490 J **


 * 2. Work then GEP then Kinetic then work again. **
 * 3. You would have to count the paces and see where the maximum height is and look at its displacement. **
 * 4. If someone believes that a law of physics is invalid or can be violated they should have to proof themselves. In order for a theory to become a law it has to be proven many times to the chance of this person being correct are slim. They should have to conduct tests in order to prove their accusation worthy of a look. Then they should find someone knowledgeable of the topic to further look it over. This would start out being their burden, but it would eventually become others as well. **
 * 5. They can increase their speed (kinetic energy) and also increase the bend in their knees.Increase the force and decrease the mass. **
 * 6. **
 * W= f Xd **
 * W=1N X1m= 1J **
 * W=1NX10m= 10 J **
 * W= 10N X 1m= 10 J **
 * W=.10N X 100 m= 10 J **
 * W=100N X.10m= 10J **


 * 7.W=GPE **
 * W=1N X1m= 1J **
 * W=1NX10m= 10 J **
 * W= 10N X 1m= 10 J **
 * W=.10N X 100 m= 10 J **
 * W=100N X.10m= 10J **


 * 8. KE=GPE **
 * W=1N X1m= 1J **
 * W=1NX10m= 10 J **
 * W= 10N X 1m= 10 J **
 * W=.10N X 100 m= 10 J **
 * W=100N X.10m= 10J **


 * 9. W= fXd **
 * W=50N X43m= 2150 J **


 * 10. KE = 1/2mv^2 **
 * KE = 1/2(62)(8.2)^2 **
 * KE = 2084.4 J **
 * 11. 6 m/s **
 * b) 563 **


 * 12a. W = F xd **
 * 40000 = 3200 x d **
 * d = 12.5 m **
 * 12b. W = KE **
 * 40000 = 1/2mv^2 **
 * 40000 = 1/2(1200)v^2 **
 * 66.67 = v^2. **
 * 13. KE = W **
 * 1/2mv^2 = W **
 * 1/2(.15)(40)^2 = W **
 * W = 120 J **
 * 14. W = KE **
 * F x 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 **
 * 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 **

Physics Plus: 1a) GPE=KE mgh=1/2mv^2 (9.8)(20)=1/2 mv^2 196=1/2 mv^2 392=v^2 19.8=v 1b) The mass of the car does not matter because they cancel out on both sides, because objects in free fall fall at the same rate regardless of mass. You need the roller coaster to work no matter what the weight of the people in the carts are.

2. EPE+GPE=KE 1/2 kx^2+mgh=1/2mv^2 v=4.2

3. GPE=KE 200(9.8)h=1/2(200) h=20 m What do you think now? Athletes do not defy gravity. This is because the figure skater is always moving while they are in the air, even if it is very small and hard to see, they are still moving. Its just that the movement is very slight so it is hard to see. All of the energy that the figure skater got from the work as well as the kinetic energy allows them to push themself into the air because the law of conservation of energy is still there.