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Jordan Rosenberg's Wikilog toc Period 6 CP Physics - Mrs. Burns - 2010

Chapter 2 - Section 1
A boy running fast to kick a ball, it goes farther than the boy that doesn't run. A bug trying to push a ball, it isn't big enough to move it. A mouse is also trying to move the ball, since it is a little larger than the bug it can move it, but not very much.
 * __What Do You See? 1__**


 * __What Do You Think? 1__**
 * 1.** Ice has less friction, it takes less effort to move across a surface with little friction, the skates are also thin, it needs less surface to push off of. Momentum keeps the person moving.
 * 2.** A soccer ball continues to roll because there isn't that much of a force acting on it. Once an object is in motion there has to be an opposite force acting on it.

Initial height: 6 meters. Highest point of skater: 6 meters The ball went the same height on both sides The results are the same as my hypothesis b.Stays the same c. They always end at the same spot that they get released because it doesn't have enough momentum to go any further than the starting point d. No
 * __Investigate: Newton's First Law__**
 * 1. Hypothesis:** When it is released from the top it should be at the same height on the other side
 * 2. Hypothesis:** The highest point will be at the same point on the other side because the slope has changed.
 * 3.** The prediction was the same. The vertical heights are equal
 * 4. Hypothesis:** the ball will still start and end at the same height.
 * 5. Hypothesis:** the ball won't stop, the ball will roll until something gets in the way, I don't think it will reach the same height.
 * 6.** The length is longer

Galileo was an Italian physicist, mathematician astronomer, and philosopher. Galileo is called the father of modern science. Inertia is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. 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. Frame of Reference- the vantage point in which the position/motion of an object is described from. Inertia is a __PROPERTY__ of matter. --- That measures the resistance to changes in an object's motion --- MASS is how we measure inertia -- Kilogram is base unit in physics --- Weight is how much gravity pulls on a mass
 * __Physics Talk 1__**

1. Inertia is the natural tendency of an object to remain at rest or to remain moving at constant speed in a straight line. Measures resistance to change in motion 2. 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. A force needs to act on an object to stop it from moving at a constant speed. 4. Friction 5. When 2 different masses are given the one with the lesser mass will move faster, therefore the one with greater mass has a greater inertia. 6. It is important to establish a frame of reference when throwing a ball in a moving train because without doing so the speed of the ball will be far greater than its true speed. When throwing a ball in a moving train the train's speed is added to that of the balls. If you know the trains speed you can subtract that from the result to find the speed of the ball.
 * __Checking Up 1__**

1.) a. The ball will roll indefinitely b. the ball wants to reach its initial height, since it can't reach that height it keeps rolling 2.) 20 cm 3.) No nothing is frictionless on Earth. 4.) The puck goes at a constant speed once it gets hit, when it hits something else, like another stick or a wall, it stops. 5.) 2.5 m/s + 4.5 m/s = 7 m/s 6.) 10.3 m/s + 4.2 m/s = 14.5 m/s 7.) a. 5.6 m/s + 2.4 m/s = 8 m/s forward b. 5.6 m/s - 2.4 m/s = 3.2 m/s forward c. 2.4sq + 5.6sq = 37.12........ sq root of 37.12 = 6.1 m/s at 67 degrees from perpendicular __OR__ 23 degrees from train direction 8.) 85 m/s - 18 m/s = 67 m/s 9.) a. 15 / sin45 = 21.2 cm b. 15 / sin20 = 43.9 cm c. 15 / sin15 = 58 cm d. 15 / sin5 = 172 cm 10.) a. In soccer when the ball is in motion it stays in motion until someone kicks it or it hits the net or something else. In hockey when the puck is hit it stays in motion until it hits someones stick or the net or something else. In bowling the ball stays in motion until it hits something, the pins, however, stay at rest until they are hit.
 * __Physics To Go 1__**

The ice skater keeps moving with very little effort because Newton's first law states that an object in motion stays at motion until a force acts upon it. The same reasoning applies to the soccer ball. The ice also has less friction therefore it also takes even less effort to move on it.
 * __What Do You Think Now? 1__**

__Baseball:__ Players don't slide into first base because you are allowed to run through the base but you are not allowed to run through 2nd and 3rd base. When running you go faster so running to first is better. If you ran to 2nd or 3rd base you'd have to slow down because you can't step off of the base, if you slide there you're foot will hit the base and stop, that is the equivalent of slowing down and it also helps to stay lower. If you run there you will go too far over the base because there is nothing to stop you from moving. Cite: http://en.wikipedia.org/wiki/Baseball
 * __Inquiring Further 1__**

Chapter 2 - Section 2
On top there is a boy, he seems to be very relaxed and tired, therefore he is walking very slowly, I know this because his shoes make imprints in the ground after every step and all of the imprints are close together. On the bottom the same boy seems to be in love and bringing flowers to someone so he is running to get there fast, I know he is running because the imprints are further apart.
 * __What Do You See? 2__**

__**What Do You Think? 2**__ When something is going 100 mi/h or 45 m/s that means in 1 hour that object can travel 100 miles in a straight line, assuming there are no forces acting on it (inertia), in 1 second that object can travel 45 meters in a straight line, assuming there are no forces acting on it (inertia).

average velocity: rate at which distance is traveled; only used when there is constant speed or when they want the average Final + initial / 2 change in velocity (final - initial) / time final = initial + acceleration x time unit for velocity = m/s!! km/h mi/h unit for acceleration = m/s sq when signs of v and a are the same, increasing speed
 * __Physics Talk 2__**

1. constant: all dots are equal distance, positive acceleration: start closer together ends farther apart, negative acceleration: start far apart and get closer 2. 8 m/s 3. instantaneous: speed at 1 point, also smaller interval; average speed: speed throughout trip 4. average acceleration 100 = 0 + a(0.0028) a = 35,714.29 m/s sq
 * __Checking Up 2__**

1. Instantaneous speed is the speed at single instant or second. Average speed is the average of several speeds/instances. 2a. Vav = d/ t ; 1000m/15s ; Vav = 66.7 m/s 2b. Vav = d/ t ; 84m/6s ; 14 m/s 2c. Vav = d/ t ; 9.6 km/ 2 hr; 4.8 km/h 2d. Vav = d/ t ; 400km/4.5h; 89 km/h 3a. Negative acceleration (slowing down) 3b. positive acceleration (speeding up) 3c. no acceleration 3d. negative acceleration 3e. no acceleration 3f. no acceleration 4a. graph with a constant increase in speed: a, d 4b. graph with a constant speed: b 4c. graph with a greatest change in speed: a, 4d. graph with an increase then a decrease: c 4e. acceleration of: student a: positive constant student b: no acceleration student c: increasing and then decreasing student d: positive acceleration 14. sports with similar ticker-tape patterns a. constant at an average speed: hockey when puck is hit b. constant at a fast speed: running c. constant at a slow speed: putting in golf d. positive acceleration: racing; start slow get faster e. negative acceleration: marathon, start fast end slower
 * __Physics To Go 2__**

When something is going 100 mi/h or 45 m/s that means in 1 hour that object can travel 100 miles in a straight line, assuming there are no forces acting on it (inertia), in 1 second that object can travel 45 meters in a straight line, assuming there are no forces acting on it (inertia).
 * __What Do You Think Now? 2__**

Chapter 2 - Section 3


__**What Do You Think? 3 **__ A force is something that acts on an object. A push or a pull There is a much larger area for the force to affect when hitting a bowling ball so it will go much less distance. Tennis ball has a smaller mass than a bowling ball so it can go further even though the same amount of force is being applied.

__**What Do You See? 3 **__ Boy is pushing a ball, starts slow and gets faster, then he gets faster, the ball doesn’t leave the stick, it’s harder as he gets faster.

__**Physics Talk 3**__ Equation for Newton's Second Law of Motion: Acceleration = force / mass a=F/m ; F=ma ; m=F/a __Where There's Acceleration, There Must Be an Unbalanced Force__ -2nd law: Accelerations are caused by unbalanced forces -if you observe an acceleration (change in velocity), then there is a unbalanced force causing the acceleration -a force to an object with a small mass, the acceleration is large -a force to an object with a large mass, the acceleration will be smaller -acceleration gets less and less as the mass gets larger and larger -even when it seems acceleration is zero, that is not true because Newton's law is always valid -acceleration of an object is directly proportional to the applied force and inversely proportional to the mass Sample Prob: As the result of a serve, a tennis ball (mt = 58 g) accelerates at 430 m/s^2 for the very bried time it is in contact with the racket F = mt(a) = (.058)(430) = 25 N __Significant Figures__ -zero between nonzero digits - yes -zero at the end of a decimal number - yes -zero at the beginning of a decimal - no -large number w/o a decimal point - no Gravity, Mass, Weight, and Newton's Second Law weight: the vertical downward force exerted on a mass as a result of gravity equation: Fgravity = (m)(Agravity) ; W = mg m = kg ; g = acceleration due to gravity __Balanced and Unbalanced Forces__ -when two forced act at the same time, the direction as well as the magnitude of the forces determine the motion of the object -the the forces are in the same direction, then the sum of the forced or net force could be zero and there would be zero acceleration -free-body diagram: a diagram showing the forces acting on an object -when you hold an object in your hand, it does not move or accelerate downward. There is the force of your hand pushing up on the object UP: force of hand on apple DOWN: force of gravity on apple -car on highway: force of the road on the tires moving it forward. force of air resistance is applied against the vehicle.

__**Checking Up 3**__ 1. Newton's second law of motion is acceleration is equal to the force divided by the mass. 2. The greater the mass, the smaller the acceleration of the object. 3. If an object weighs 30 N. Weight is the vertical downward force exerted on a mass as a result of gravity. The force is 30 N. 4. On a planet with a higher acceleration, your weight would increase, but your mass would remain the same.

1) See textbook for table 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 5) a. Newton's first law of motion: A bowling ball has a larger mass than a baseball, therefore the inertia is greater. A greater force than a human would need to throw the bowling ball really fast so it continues at a fast speed. The baseball has less inertia but will travel in a straight-line of motion for longer and a greater force because it is easier for the force of the human bodies to accelerate it. 5b. Newton's second law of motion: In the equation F = ma, Mass and acceleration are indirectly proportional. A baseball with less mass will have a faster acceleration than a bowling ball, therefore it is going faster when it hits your hand. You need to put more force on a bowling ball because its mass is much larger. 9) When throwing a ball, the force of your hand is acting on the ball until an unbalanced force comes in contact with it. 10) 50N + 40N = 90N 11) 4a x 200N each = 800N the net force is 4 times 200. 800N is needed to get the car out of the mud. 12) F = am. 125N = a x 0.7kg. 179 m/s sq 13) 120 sq (north) + 50 sq (east) = 16,900. sq rt 16,900 = 130. tan-1 (120/50) = 67.38. 130N @ 67.4 degrees NE 14) 4,000 sq (south) + 5,000 sq (east) = 41,000,000. sq rt 41,000,000 = 6403.1. tan-1 (4,000/5,000) = 38.66. 6403N @ 39 degrees 15) F = mg. F = 12.8kg x 9.8 m/s sq. F = 125N 16) a. 30 sq + 40 sq = 2,500. sq rt 2,500 = 50N. 50N @ 53 degrees b. F = ma. 50 = (5.6)a. a = 8.9 m/s sq 17) a. 30 sq + 20 sq = 1,300. sq rt 1,300 = 36.1. 36N @ 34 degrees b. F = ma. 36.1 = (100)a. a = 0.36 m/s sq c. 30N + 20N = 50N. F = ma. 50 = (100)a. a = 0.5 m/s sq 18) The soccer ball, which weighs 0.45kg, was kicked at and accelerated at 40 m/s sq. The player kicked the ball with a force of 18N. That's an incredible amount of force
 * __Physics To Go__**

**__Physics Plus__** 1) 125 sq (north) + 125 sq (south) = 31,250. sq rt 31,250 = 177N. tan-1(125/125) = 45. 177N @ 45 degrees NW 2) a. 70N (south) - 40N (north) = 30N south b. 30 sq (south) + 40 sq (west) = 2,500. sq rt 2,500 = 50. tan-1 (30/40) = 36.9. 50N @ 36.9 degrees SW c. Southwest

A force is a push or a pull. There is a much larger area for the force to affect when hitting a bowling ball so it will go much less distance. Tennis ball has a smaller mass than a bowling ball so it can go further even though the same amount of force is being applied. Since mass and acceleration are indirectly proportional the same amount of force placed on something with more mass would have a lesser effect that that amount of force being placed on a smaller object. The object with a smaller mass would have a higher acceleration.
 * __What Do You Think Now?__**

Chapter 2 - Section 4
**__What Do You See?__** The apples are evenly placed horizontally. One is going straight down the other is out more. A boy is in between both timing them.

**__What Do You Think?__** The velocity, mass, max height, force, direction, and distance to the ground and from the starting point all determine how far an object thrown into the air travels before landing.

**__Investigate__** __Part C__ 1) it stayed the same 2) it increased 3) it increased 4) it increased 5) initial height 6) initial height, initial velocity

Trajectory - path Projectile - an object acted on ONLY by gravity The x-component and y-component of all vectors are independent .....Vertical velocity affects vertical distance (y-axis) .....Horizontal velocity affects horizontal distance (x-axis) Time for a horizontally launched projectile to hit the ground (hang time) is the same as the time it takes to drop <span style="font-family: Arial,Helvetica,sans-serif;">Acceleration due to gravity is -9.8 m/s sq <span style="font-family: Arial,Helvetica,sans-serif;">.....Gravity is vertical, therefore it only affects the y-axis <span style="font-family: Arial,Helvetica,sans-serif;">Y velocity is always 0 at maximum height <span style="font-family: Arial,Helvetica,sans-serif;">Launching horizontally results in the same trajectory at the second half of the ball thrown at an angle
 * __Physics Talk__**

<span style="font-family: Arial,Helvetica,sans-serif;">1) Yes, with the acceptance of air resistance things drop at the same speed 2) No, it increased by 9.8 m/s every second 3) Velocity is 0, acceleration is -9.8 m/s sq
 * __Checking Up__**

1-2) <span style="font-family: Arial,Helvetica,sans-serif;"> 4) Mom - the dropped bullet would hit the ground first Dad - both the fired bullet and the dropped bullet would hit the ground at the same time Matt - the dropped bullet would hit the ground first Brett - the dropped bullet would hit the ground first 6) It's horizontal motion wasn't affected by gravity but the vertical motion was..... vertical motion wasn't affected by speed of the chair but the horizontal motion was. 7) Both arrows will take the same time to strike the horizontal plane 8-10) 8) 3.6 m/s @ 33.7 degrees 9) 11.98 m/s 9b) 23.96 m/s 10) 8.5 m/s 10b) 4.25 m/s 11) The pitcher just threw the baseball at a 25 degree angle above the horizontal at a velocity of 80 m/s from the ground. It has no acceleration horizontally, but vertically it has an acceleration of -9.8 m/s/s. The time it took to reach the batter was 3 seconds. After these three seconds, the ball was traveling at 72.5 m/s.
 * __Physics To Go__**

1-2)
 * __Physics Plus__**

<span style="font-family: Arial,Helvetica,sans-serif;">The velocity, mass, max height, force, direction, and distance to the ground and from the starting point all determine how far an object thrown into the air travels before landing. On top of this I believe gravity affects how far an object goes as well.
 * __What Do You think Now?__**

1. When throwing the ball goes up at an angle correspondent to the speed it was up and the speed it is thrown out. The speed the person is running affects its horizontal velocity and the velocity it is thrown at affects the vertical velocity. Gravity also affects the vertical velocity on the way down. 2. I don't believe that, in this case, the shape of the object doesn't affect the trajectory. Other than of course the ability to grip it. I feel this way because it doesn't move after touching the ground, it just stops there.
 * __Video and Questions__**- Shot put

Chapter 2 - Section 5
A girl kicked a ball in the air, it bounced off a boys head and went into the goal but it was at a different (lesser) angle than when the girl kicked the ball, since the angle was less it didn't go as high.
 * __What Do You See?__**

At a lesser angle the projectile will not go as high as it would if the angle was larger. With a larger angle the projectile will go much higher than it would go farther. A greater launch speed would cause the projectile to go farther if at the same angle with a lesser launch speed.
 * __What Do You Think?__**

__**Physics Talk**__ A projectile has two motions that act at the same time and do not affect one another - One motion is constant along a straight line (affected by launch speed and direction) - The other is downward acceleration at 9.8 m/s sq. (affected by launch) Mathematical Model: table of times, speeds, and distances during falling Physical model: the evenly spaced strings of calculated lengths Without air resistance, all trajectories are parabolas All balls travel in parabolas - A 45 degree launch produces the greatest range (longest distance) -Complimentary angles travel the same distance Angles smaller than 45 have greater horizontal velocities but are up for a shorter amount of time Angles larger than 45 have smaller horizontal velocities but are up for longer amount of time Exceptions: curve balls, temperature

__**Checking Up**__ 1) Two types of motion: constant and downward acceleration. 2) For a model to be accepted, it must match the reality in nature. 3) Height and range with different angles: a 45 degree launch produces the greatest range, pairs of angles (add up to 90) are identical distances.

1) 45 degrees because the object will go the farthest. 2) When greater than 45 degree angles, the less far the object will go. 3a) 90 degrees- 30 degrees = 60 degrees 3b) 90 degrees- 15 degrees= 75 degrees 4) It is a human error because it is not possible to launch yourself at a 45 degree angle. Initial x velocity is greater than initial y velocity. The angle is much less than 45 degrees. 5) When you jump high, you are good at the jump, thats why he was probably good at it because longer time spent in the air = more distance. When initial x velocity is greater his max y distance is high. 6a) a = -g = -9.8 m/s/s down 6b) Max velocity equals initial x velocity because y velocity equals 0 at its max height.
 * __Physics To Go__**

7a) Vf = 29.4 m/s 7b) Horizontal speed = 5 m/s 7c) Distance from cliff = 15m 8) The longest range is obtained at 45 degrees 9) The angle closest to 90 degrees would give you the largest height 10a) The direction of acceleration is down 10b) Time to reach = 4.5s 10c) Distance from cliff = 90m

1-2) 1) Horizontal distance = 8.26m 2) Horizontal distance = 49.5m
 * __Physics Plus__**

as angle is increased the range increased, when the angle is 45 degrees is larger hang time is larger but range is smaller. Complementary angles have same range for ground-to-ground launch. Max range is at 45 degrees (also only for ground-to-ground launch. The greater the speed the further it will go.
 * __What Do You Think Now?__**

Chapter 2 - Section 6
__**What Do You See?**__ I see a person that is on a chair that has wheels on it with his feet on the wall. He is pushing off the wall and flying back at a fast speed with the chair on the floor and he is still in it.

__**What Do You Think?**__ If i were to tell someone how to jump, I would tell them to stand straight, bend their knees then push off the ground so the force would push them forward using gravitational force. (I might also tell them to take a running start as well)

__**<span style="font-family: Arial; font-size-adjust: none; font-size: 13px; font-stretch: normal; font-style: normal; font-variant: normal; line-height: 19px; margin: 0px;">Physics Talk **__ Newton's Third Law of Motion: - For every applied force, there is an equal and opposite force. The two forces always act on different objects - Forces are always equal in the opposite direction - Forces come in equal and opposite pairs - Push on the wall and the wall pushes back with the same force and you can't make the forces unequal Inanimate Objects can Push Back: - Objects can apply force due to mass and gravity. - Free body diagram: a diagram showing the forces acting on an object - When standing, your mass is pulling you down. If not for an equal force from the floor that was going up, you would fall down. Challenging Newton's Third Law how something/someone can Pull something/someone ex: person on wheely chair person pulls on chair w/ small force. The chair pulls back on person with equal small force. The one force on the chair makes it move forward. Two forces on the person--one of the ground and other of chair, which are not equal. Ground force is larger making the person move forward

__**Checking Up**__ 1. Newton's 3rd law of motion: if you push or pull on something, it will push/pull back with equal force in the opposite direction. Forces come in pairs and act on different objects. 2. Earth pulls down a mass with a force of gravity. The mass pulls up on the Earth with an equal force of gravity. 3. A free-body diagram shows the forces acting on an object.

__Newton's Laws of motion__ 1. An object at rest will stay at rest, and an object in motion will stay in motion at constant speed in a straight line, unless an unbalanced force acts on it (things wont change motion unless forced to do so) 2. Acceleration is directly proportional to net force and indirectly proportional to the mass of the system (a = F/m) 3. Every action has an equal and opposite reaction (All forces come in pairs but act on 2 different systems)
 * __General Notes__**

__**Physics To Go**__ 1) Yes, because every action has an equal but opposite reaction. 2) No but "restoring" forces balance downward weight. 3) The bathroom scale measure weight / force by the simple equation of m times gravity. It measures the mass of the body exerting a force on the scale and multiplies it by the acceleration of gravity on Earth. Spring with needle attached, calibrated. 4) The forces on each other are the same, but the acceleration of the ball is much greater than the bat. The accelerating ball collides with the bat, which may have a lower mass, and break it. Equal but opposite. The bat breaks because Fball is too big for material to withstand. 5) When a big football player hits a small running back they are both exerting the same force on each other. But, since the mass of the running back is smaller, and the acceleration of the bigger player is larger, the smaller guy will move into the direction that the larger guy was going. Equal but opposite, the smaller player has bigger acceleration. 6) Normal force of person on boards and boards on person. And weight of the person to Earth and boards to Earth. There is no friction because of the ice. boards on player = - player on boards. 7) Baseball players prefer to wear gloves when catching a ball because the padding of the glove lowers the balls acceleration, this will reduce the force on the hand. 8a) The player just slammed into the boards. He exerted a large force on the boards going at a high acceleration. The boards exerted the same force, but has a larger mass which made the player stumble a little. But, the force of the player's weight was strong enough to keep him on the ground. There was no friction because hockey is on ice, which is too slippery! 8b) A deflection of the ground can produce a force if you were to fall. During the fall, you would be pulling up the force from the ground while pushing down the force of your own. I would make this more exciting by showing a clip of a soccer player tripping, and falling and commenting on it with enthusiasm.

You are pushing, or applying force, downward at the ground, the ground is applying force upwards on you. They should bend their knees to give themselves more of a push downwards. If I were to tell someone how to jump, I would tell them to stand straight, bend their knees then push off the ground so the force would push them forward using gravitational force.
 * __What Do You Think Now?__**

Chapter 2 - Section 7
The boy is pulling the shoe, since there's ice there isn't friction so its easier to pull, the hes at the beach doing the same thing, its much harder because there's more friction
 * __What Do You See?__**

Different shoes have different traction, grass, like in soccer, you want shoes that will help grip the ground so you don't fall as easily. The type of shoe that you wear makes a very big difference in your balance and mobility along the given surface.
 * __What Do You Think?__**

__**Physics Talk**__ Analyzing the Forces Acting on the Shoe - Friction: a force that resists relative motion between two bodies in contact - 2nd law: vertical forces on the shoe must add up to zero The downward force of gravity on the shoe must be the same as the upward force applied to the shoe by the surface Normal force: the force acting perpendicularly or at right angles to a surface (equal in force and opposite in direction to the shoe's weight)

1) The force of friction is equal to the force reading on the spring scale because the pulling force applied was equal to the frictional force, and since the two forces were in opposite directions, the net or total force due to them was zero 2) Coefficient of sliding friction has no units because it is a force divided by a force 3) The force of friction is = force required to slide the object on the surface with a constant speed
 * __Checking Up__**

<span style="font-family: Tahoma,Geneva,sans-serif;">1) In basketball, athletes want to have more friction to have better footing. If it is raining outside, or the court is icy, the athlete would want to increased the friction. They should buy some type of shoe with a heavier mass because with a heavier mass this will create more friction. <span style="font-family: Tahoma,Geneva,sans-serif;"> 2) In snowboarding, athletes want to have the least amount of friction. To reduce friction, they wax the bottom of the board to reduce friction. <span style="font-family: Tahoma,Geneva,sans-serif;"> 3) No, she will not know if her shoes will provide the same amount of friction on a court outside of her home. She needs to know the material of court, the roughness, and how it will react with your sneakers. <span style="font-family: Tahoma,Geneva,sans-serif;"> 4) Tennis players have different shoes for clay, grass, and hand surfaces. For the hard surfaces, their shoes don't need to provide as much friction. On the clay courts, which are more slippery, the shoes need to provide more friction. For grass, the shoes need to provide less friction. <span style="font-family: Tahoma,Geneva,sans-serif;"> 5) .03 = x/600 N . The minimum horizontal force would have to be 18N to keep the skier moving at constant speed across level snow. 6a) W=mg ; W=(1000)(9.8) ; W=9800N 6b) µ=f/N ; .55=f/9800 ; f=5390N 6c) Fx=MAx ; f=ma ; -5390=1000a ; a= -5.39 (m/s)/s 6d) Vf=Vi+at ; 0=Vi+(-5.39)(6) ; Vi = 32.34. Change in speed: 32.34 m/s 6e) Original speed: 32.34 m/s. The driver's was not telling the truth. He was going faster than he should have been driving: 32.34 m/s and he said he was driving 29m/s. 7) Air or water does have affects on motion similar to sliding friction. Air resistance and water resistance remain constant, but it is the speed that is changing. When I am running and increasing speed, the same wind resistance is hitting my face. More resistance with more speed. 8) If there is a max force it will set a limit on how fast you can start. Even if you have strong legs, it won't have more acceleration. To solve this problem, we can reduce friction by buying shoes that have a smoother surfaces. 9) Extra credit 10) Friction is important to running, baseball, soccer, and other sports. Cleats are used because you need friction to keep the players footing good and dug into the ground.
 * __Physics To Go__**

1.
 * __Physics Plus__**

1) The coefficient of friction in Part I displays the friction/forces against each other between the block and the floor. 2) My µ was .375 and the class µ was .325. The percent difference is 23.08%. The results do not have to be the same because of random errors or systematic errors. The results, however, should be similar 3) My percent error was very high. 4) The theoretical physics we are doing in class applies to the real world because most sports we play display this Newton law. Bowling for example, contains the coefficient of friction. My answers "disproved the theory... way to go Jordan" 5) 3 sources of experimental error: if the tape measure was on a slant, the distance could be thrown off. If the the floor has bumps, it can throw off the acceleration. Finally, if the stop watch was not stopped/started quick enough, the calculations for part II would have errors. Timing could have also been off a lot. The block could've bounced as well.
 * __Lab: Bowling With Blocks__**

N || µ || Class Avg. µ || % Difference || Part II Fy = MAy ; N-W=0 ; N=W ; W=(.176)(9.8) ; W=1.72N µ=f/N ; .25 = f/1.72 ; f=0.43N -0.43 = .176a ; a = -2.4 m/s/s Fx = MAx ; f=MAx ; .43=.176a ; 2.4 (m/s)/s=a Vf^2 = Vi^2 +2ad ; -Vi^2 = -27.65; Vi = 5.3 m/s Vf = Vi + at ; 0 = 5.3 + (-2.4)t ; t = 2.2s
 * Tension N || Tension N || Tension || NFf(N) || Total Weight
 * 3 || 3 || 3 || 3 || 12 || .25 || .325 || 23.08 ||
 * Mass (g) || Mass (kg) || Measured Time (s) || Measured Distance (m) || Ff (N) || Acceleration (m/s)/s || Calculated Vi (m/s) || Calculated time (s) || % error ||
 * 176 || .176 || 2.25 || 5.76 || .43 || -2.4 || 5.3 || 2.2 || 2.3 ||
 * 176 || .176 || 2.1 || 9.44 || .43 || -2.4 || 6.7 || 2.8 || 25 ||
 * 176 || .176 || 2.2 || 8.58 || .43 || -2.4 || 6.4 || 2.7 || 18.5 ||

%diff = (I avg - your I / avg) x 100

Different sports require different shoes because the amount of friction varies on different surfaces. More friction gives you better footing. Different features of the shoe affects how you play. The tread on the bottom can change the amount of friction. The coefficient of friction affects how much friction there is between you and the ground.
 * __What Do You Think Now?__**

Chapter 2 - Section 8
A pole-vaulter trying to get on top of a 20 foot high building. It shows that he is accelerating a lot in order to make it.
 * __What Do You See?__**

The height is a lot larger on a 12m than a 6m, just because the pole went from 5.5m to 11m doesn't mean the height still works. Other variables definitely come into play. Factors that limit the height of a pole vaulter could be the length of the pole, and the vaulters speed and acceleration.
 * __What Do You Think?__**

a. I had the ruler off of the desk a small amount but i applied a lot of force. b. The factors that affect its height are the amount that the ruler sticks out and the force applied as well as the position of the penny, other factors are the flexibility of the ruler and how high above the ground the ruler is. The closer to the end the higher it goes. 1a) The effect the position of the penny on the ruler has on the pennies height b) The height of the penny at different positions on the ruler c) A meter stick d) I will compare the 3 position's heights
 * __Investigation__**

Trials: Conclusion: When the position of the penny was closer to the edge of the table, the height of the penny was lower than when the position of the penny was further away from the edge of the table.
 * Force || Ruler sticking Out || Position of Penny || Height of Penny ||
 * 2 cm || 11 cm || 2 cm out || 24 cm ||
 * 2 cm || 11 cm || 5 cm out || 33 cm ||
 * 2 cm || 11 cm || 7 cm out || 49 cm ||

Law of Conservation of Energy a force can change the position and speed of an object in a way that allows the position and speed to change back Kinetic energy- energy associated with motion gravitational potential energy- energy an object possesses because of its vertical position from Earth potential energy- energy associated with position SUM of potential and kinetic remains constant 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 Energy and Work while a ball is rising or falling, the sum of gravitational potential and kinetic energy remains constant work- the product of the displacement and the force in the direction of the displacement (physics quantity that equals the force multiplied by the distance) Conservation of Energy in the Pole Vault elastic potential energy- the energy of a spring due to its compression
 * __<span style="font-family: Arial; font-size-adjust: none; font-size: 13px; font-stretch: normal; font-style: normal; font-variant: normal; line-height: 19px; margin: 0px;">Physics Talk __**

1. A force is the reason for a change in energy. 2. The penny gets its energy from a ruler that has elastic potential energy. 3. The vaulter's kinetic energy is used to catapult him with an initial speed upward and the remaining kinetic energy is turned into elastic potential energy as the pole bends. 4. Joules is the unit of energy
 * __<span style="font-family: Arial; font-size-adjust: none; font-size: 13px; font-stretch: normal; font-style: normal; font-variant: normal; line-height: 19px; margin: 0px;">Checking Up __**

4) The length alone doesn't determine the limit of vaulting height. Speed has a very major impact on the height. 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(sq) = mgh. 1/2(v)(sq) = (9.8)(4.55). = 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. 8) GPE = KE. mgh = 1/2mv(sq). gh = 1/2(v)(sq) 9) EPE = KE. 1/2kx(sq) = 1/2mv(sq). 10) EPE = W. 1/2kx(sq) = W. 1/2kx(sq) = F x d. 11) GPE = EPE. mgh = 1/2kx(sq). 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 = KE = GPE. 15) The baseball is initially at rest. It then is hit by the bat which does work which is made into kinetic energy until reaching the highest point, then it transforms into gravitational potential energy and the net and ground make the ball come into rest. 16) Soccer: the ball is moving at an increasing speed, with its kinetic energy, the ball is kicked up. this happens to the highest point and then kinetic energy transforms into gravitational energy.
 * __Physics To Go__**

The person's speed is a very important factor in the height. The speed is what matters, not the length of the pole. The more velocity you having the more kinetic energy which makes a larger gravitational energy. Speed, the deflection of the pole, and their height limit the height a pole vaulter can go.
 * __What Do You Think Now?__**

Chapter 2 - Section 9
__**What Do You See?**__ An ice skater spinning fast and jumping really high, someone in a helicopter is timing them.

The hang time of athletes does not defy the law of gravity, I think it bends it. The athlete stays up longer than usual but they still do come back down. No, once again, they aren't defying it but just bending it. The amount of speed and torque they have allows for the hang time.
 * __What Do You Think?__**

__Prelab:__ 2) 20 frames 3) 20 x (1/30) = 2/3 of a second 4) No, just not as noticeable, the differences in height are very small, the change in positions of the legs makes it seem not to be moving. 5) 31 frames x (1/30) = about 1 second __Questions:__ 1) Bend your knees (A- pushing off floor), unbend knees (A- pushing off floor, B- gravity), airborne(B- gravity). During stage A there is Work and in stage B there is gravity. 2a) Force it takes to jump 2b) Height and Normal Force (mass x gravity) 2c) A meter stick, and data studio 2d) W = GPE..... W = mgh. mg = 64.4kg (9.8). NF = 631.12N. GPE = mgh. GPE = 631.12 (.36). GPE = 227.2J... F x D = 227.2J. F(.15) = 227.2J... F = 1,514.67N Calculated Force: 1,514.67N 4) Actual Force: 1,420.67N 5) My calculations were pretty close, i didn't take into account the fact that i have shoes and other stuff on. (94/1420.67) x 100. Percent error = 6.6%
 * __Investigate__**

__**Physics Talk**__ Conservation of Energy jump chart^ in ready position about to jump, you have EPE from contractions in muscles. launch position has both GPE and KE energy of all positions of a jump are equal the greater the peak position, the greater the GPE potential energy from height jumping would provide kinetic energy when you land. when going down, you continue to have kinetic energy bc you would be losing GPE. The trampoline stretches & gains EPE at the expense of KE and changes in GPE example: all energy can be measured or calculated conservation on energy: total of all energies at any one time must equal the total of all energies at any other time collision between a player's foot and soccer ball, the ball can gain KE and move faster. Whatever the ball gained in energy, your foot lost that energy. No matter what is lost or gained, the total energy remains the same
 * [[image:proringer:PeRrIEoSEthree.png height="132"]] ||
 * [[image:proringer:idontgetthishehe.png]] ||

Checking Up 9 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

1) W = GPE W = mgh W = 50(9.8)1 W = 490 J 2) Bobsled run. W > KE > W 3) People would go about seeing if the statement is correct by making lines where the player's foot is during each frame. There they will see that the player does not actually hang in the air, but his maximum heights have little displacement therefore it results in people assuming that there is hang time. 4) If someone where to claim that a law of physics can be defied, they should give total proof of their information. Afterwards, someone else who is more knowledgeable and also has run many tests on the subject, can prove that the claim is not true. Therefore, both of them have the burden of proof. 5) An athlete can increase their jump by bending their knees more and swinging their arms more which both increase in electric potential energy and will increase KE and GPE. 6) W = F x d a) 1N x 1m = 1J b) 1N x 10m = 10J c) 10N x 1m = 10J d) .1N x 100m = 10J e) 100N x .1m = 10J 7) W = GPE a) 1N x 1m = 1J b) 1N x 10m = 10J c) 10N x 1m = 10J d) .1N x 100m = 10J e) 100N x .1m = 10J 8) KE = GPE a) 1N x 1m = 1J b) 1N x 10m = 10J c) 10N x 1m = 10J d) .1N x 100m = 10J e) 100N x .1m = 10J 9) W = F x d 50 x 43 2150 J 10) KE = 1/2mv^2 KE = 1/2(62)(8.2)^2 KE = 2084.4 J 11) a = F/m a) 6 m/s sq b) 563J 12a) W = F x d 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. v = 2.7 m/s sq 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 vaulting: running, pole on ground bending, peak height, landing, collapsing... sum is always the same, when the cushion collapses most of the energy is now work (the numbers could still be spread amongst the different types of energy). 16) Trampoline: peak height, landing on trampoline, lowest point on trampoline....sum is always the same (the numbers could still be spread amongst the different types of energy) 17) Skier: top, middle, and bottom of a slope.... the sum is always the same (the numbers could still be spread amongst the different types of energy) 18) In soccer, the ball is kicked described as work. Then it accelerates which is kinetic energy and is above ground which is gravitational potential energy. On the way down there is also kinetic and gravitational potential energy. At the end, there is friction to stop the ball, which is work
 * __Physics To Go__**

1a) GPE = KE mgh = 1/2mv^2 (9.8)(20) = 1/2 v^2 196 = 1/2 v^2 392 = v^2 19.79 = v 1b) If it's mass independent, the amount of passengers on the roller coaster will not affect the ride. 2) EPE + GPE = KE 1/2kx^2 = 1/2mv^2 1/2(60)(.40)^2 = 1/2(.3)V^2 5.99 = V 3) 20 m
 * __Physics Plus__**

No one can literally defy the laws of gravity. Hang time is the reason people stay in the air. What seems to be them staying in the air is the speed at which they are moving. When at the top of the turn they are traveling vertically at a very slow speed, giving the illusion that there is no movement at all. A figure skater doesn't defy the laws of gravity, the skater jumps off the ground at a lesser angle so their horizontal is much longer and vertical is shorter, once again giving the appearance of the defiance of gravity.
 * __What Do You Think Now?__**