Ch2_PuleoLucaslp

Chapter 2 toc

Section 1
Football Physics: The anatomy of a Hit http://www.popularmechanics.com/outdoors/sports/physics/4212171 - The article describes the hits during a football game. It shows how hard they are and as time goes, the hits get harder. It describes the distribution of weight during a hit. It also shows much it hurts to hit the ground after a hit. "At 5 ft. 11 in. and 199 pounds, Marcus Trufant is an average-size NFL defensive back (DB). Those stats don't stand out in a league where more than 500 players weighed 300-plus pounds at the 2006 training camps. But a DB's mass combined with his speed -- on average, 4.56 seconds for the 40-yard dash -- can produce up to 1600 pounds of tackling force, according to Timothy Gay, a physics professor at the University of Nebraska and author of The Physics of Football".

What do you see? - Kids running - The kids that are running kick the ball farther than the kid that is not moving - The more momentum the farther the ball will go - The more mass the farther the ball will go

What do you think? - They are using momentum to travel across the ice. The heavier you are the faster and farther you will travel. - If the ball is kicked it moves across the field because the field is flat. Because it is flat the ball can travel for a long period of time. The harder the ball is kicked the faster and longer it will travel.

Investigate

hypothesis- - The steeper the track the faster it will go. It is because it is building momentum

1. c) The height is 4.74 m.  e) The other height is 4.74 m.  2. a) He will go up farther on the other side than he initially started. b) The steeper that it is the faster he goes and the higher he travels. 3. a) He stayed the same height.  b) The height at which you start will be the same at the other end. 4. a) It will go slower because it is not going to be able to pick up as much momentum.  b) Yeah it was correct. The smaller the slope the slower the person will travel. 5. a) No because he just falls off the track.  b) It will keep on going. c) For there to be a slope or a stop at the end. d) It will cause the person to stay on the track and keep bouncing back and forth. 6. a) The slower he will go.  b) It will travel until it falls off the track. c) If the slope is equal then it will travel equal on both sides. d) It will never stop because it will glide like a skater going across the ice.

Physics Talk inertia- is a property of matter that measures the resistance to changes in an object is motion mass is how we measure inertia (kilogram is base unit in physics) Weight is how much gravity pulls on a mass

Checking up Questions 1. Inertia is the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line. 2. In the absence of an unbalanced force, an object at rest remain at rest, and an object already in motion remains in motion with constant speed in a straight line path. 3. It needs a push or pull to stop the object from moving at constant speed. 4. Gravity is working against it and it eventually stops. Friction 5. The heavier the object the farther it is going to travel. 6. It is important because the train and the ball are moving at the same speed, but when you throw the ball it has more speed added on to the original speed.

Physics to Go (your answer in red) 1. a) It will keep on traveling until a farce acts upon it to stop it.  b) It will keep on traveling forever. 2. It will travel until it hits 20 ft high on the other end. 3. No because friction can act upon it and force it to stop. 4. There is no friction acting upon the puck so the puck will not stop and keep going until something hits it. 5. 7 m/s 6. 14.5 m/s 7. a) 8 m/s forward  b) 3.2 m/s forward c) It is 2.4 m/s. 6.1 m/s at 61 degrees 8. 85 m/s 67 m/s  9.  a) 21.2 cm  b) 43.9 cm  c) 58 cm  d) 172 cm  10. a)and b) The score is 2 to 0. The man just took a slap shot and it is gliding across the ice. Since there is no friction it will not stop until it hits the net or any other objects. When you kick a soccer ball it will go until the friction stops the ball from moving. When you are taking a goal kick in a soccer game. You need to build up momentum to be able to kick the ball as far as you possibly can.

What do you think Now? - 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.

Inquiring Further 2. When you are running towards first base, you are not trying to avoid a tag. You are thinking about beating out the ball. The faster you run the quicker you get to the base. When you are going to second and third base, you are trying to get to the base as fast as possible, but also trying to avoid the tag from the opposing team. http://science.howstuffworks.com/science-vs-myth/everyday-myths/newton-law-of-motion4.htm and http://www.associatedcontent.com/article/1220026/newtons_laws_on_baseball.html

Section 2
What do you see? - I see a kid at a constant speed. The there is another kid that is running at an increasing speed trying to chase the dog.

What do you think? - 100 miles per hour is shorter because miles/hour is shorter than meters/second.

Physics to Go 1. Average speed s keeping the same consistency in your movement. Instantaneous speed is quickly increasing your speed at a rapid rate. 2. a) 1000m/15 s = 66  b) 84/6 = 14 c) 9600/120 = 80 d) 40000/250 = 160 3. a) negative  b) positive c) positive d) negative e) positive f) positive 4. a) b  b)a c)d d)c e) a is positive, b is constant, c is increase the constant, d is increasing 6.  a) It accelerated -45 km/h = -1.5 m/s2 b) It has a negative acceleration 7.  a) constant b) increasing c) constant then increase then constant again d) increase the decrease then increase 8. 50 mi/h  9. It was 0 then he accelerated to 15 and now stays at constant speed. NO  10. close dots then increasing distance between each dot  11. It is decreasing after each second. 4, 8, 12,...  14.  a) When a track athlete is running around the track for a run than is longer than 1 mile. They try to keep the same pace the entire time until the end to increase speed and win the race. b) It is the same thing when they are running around the track. c) When you play soccer you jog around at a slow constant speed until you need to pick the speed up to go get the ball. d) When a track athlete is running a 100 meter dash they gradually increase speed until they get to the finish. e) When you are playing football and you need to make a sharp turn, you need to stop and then turn which causes the negative acceleration.

Physics Talk Checking up Questions 1. a) There are continuos spaces in between the dots. It stays at that pace for a while.  b) The dots start similar and then increase as the sheet goes on. c) It starts out at bigger spaces and then they decrease as the sheet goes on. 2. The runner is traveling 8 m/s.  3. Instantaneous speed is randomly increasing speed. Average speed is running for a long period of time at different paces and then finding the average of that pace.  4. It is traveling at an average of 1 m/s.

rebounding (any object) || rebounding is when you change direction Even if speeds are small, accelerations can be huge if the bounce times are tiny
 * velocity || accelerate || example ||
 * small || small || turtle ||
 * big || big || racecar, airplane ||
 * small || big || rabbit
 * big || small || Truck ||

Physics Plus 1. -1000 m/s 2. -5 m/s2 3. a) Whole time  b) Whole time c) Whole time

Section 3
What do you see? - Three guys pushing a ball - the first guy is slow and is not working harder. As he keeps on pushing it faster it gets harder and harder.

What do you think? - It is a push or pull - The tennis ball will have more speed do to the easier to aply the force. It takes longer for the bowling ball to pick up speed because it is heavier.

Physics Talk

Checking Up 1. It is Newton's second law of motion. It is that an object will accelerate if it is pushed or pulled 2. When you increase an objects mass, the acceleration will get smaller. 3. If an object weighs 30 N. The weight is downward, so the weight stay 30 N. 4. On a planet with a higher acceleration, your weight would increase, but your mass would remain the same.

Physics to Go 1. 350 80  10  80  -15  -3000  3. 140 m/s2 4. .8 5.  a) The bowling ball is heavier than the baseball so it is going to be harder to get it started than the baseball.  b) The bowling ball will travel faster than the baseball because it is heavier, and it will also be harder to stop it. 9. The force stops acting upon the ball immediately after you let the ball leave your hand. 10.50N + 40N = 90N 11. 4 adults x 200N each = 800N 12. F=am; 125N =a(.7kg); 179 m/s2 13. 130N north @ 67 degrees NE 14. 6403N @ 39 degrees 15. F=mg F=(12.8kg)(9.8m/s2) F= 125 N 16a. 50N @ 53 degrees 16b. f=ma 8.9 m/s2 17a. 36N @ 34 degrees 17b. f=ma 36=100a 0.36 m/s2 17c. 50N = 100kga a= .5 m/s2 18. Here is the pitch. The swings the bat toward the baseball, the baseball makes impact with the bat and comes off the bat harder than it was originally thrown by the pitcher. The ball will travel farther after it makes impact with the bat, than it would when it is thrown by the pitcher.

2. a) 176N @ 45 degrees NW  b) 80 NS @ 60 degrees SW  c) Northwest

Section 4
What do you see? - There is a man that is timing the apples when they fall. There is a girl dropping ht apples at different areas.

What do you think? - The weight of the object, the amount of force applied to the object, and the height that it is thrown at. The speed it has.

Investigate

Notes for Physics talk Trajectory- path projectile- an object acted on only by gravity The x-component and the y component of all vectors are independent

Checking up questions 1. Yes because they are leaving at the same point. There is no resistance. 2. No. It increases by about 10 m/s for every second. 3. It is 0. The acceleration is 9.8. It stays the same.

Physics to Go (questions 1,2,4,6) 7. a) 34.2  b) 150*34.2 = 1530 8. I would say that two forces are on both sides pulling towards opposite ends until the other one gets tired. 9. When you let go off the ball you stopped applying force on the ball. 10. tan- = (40/40) = 45 m/s 11. tan- = (200/4) = 88.9 m/s

Physics Plus 1,2



What do you think Now? What determines how far an object thrown into the air travels before landing? - The height of the object. The weight of the object. The speed that the object is tossed at.

Reflection on the Section - The heavier and faster the object is pushed in a certain direction, that will give you the distance the object will travel. It is the height + the weight + the speed = the distance.

Section 5
What do you see? - The trajectory of the ball goes up and down. It continues that path of other people because they are applying pressure to the ball so it will continue until it hits the net. What do you think? - The first is really high, then followed by a shorter one, then a shorter one until it goes into the net. - The higher you kick it the faster it will travel down and the harder it will go after hitting another force. Physics Talk Checking up 1. The speed that the object is thrown at. The height that the object is at. 2. They must be able to supply the height, speed, and the angle that the object can be thrown at. 3. The range becomes different as you change from 10 to 80 because the higher the angle the less distance the ball will travel. The height causes the ball to go at a certain speed.

Investigate 5 with teacher RESULTS My Worksheet Physics to go #1-6 #7-10 (correct answer in red) 1. A 90 degree angle because if the angle is 90 degress then everything is equal and the object will stay in the air of the longest period of time. 2. a) Then it stays in the air longer.  b) Then it stays in the air for a shorter period of time. 3. a) 30 degrees helps it stay in the air for longer.  b) 15 degrees makes it stay in the air less and more traveling on the ground. 4. Vx > Vy They are building up speed and then launching themselves and they are aiming for distance. 5. He is so fast that it helped him greatly when trying to build up enough speed to launch himself into the air. 6. a) It is traveling east. -9.8 m/s2 down  b) The velocity is northeast. 7. Vy = Vi + at  a) 5sin(3) = 26 m/s 29.4 m/s  b) 5sin(1) = 87 m/s 50 m/s c) 7 m 15 m 8. If it was at an angle of 45 then it would travel the farthest.  9. The mass because the heavier the object is the higher it will go and the longer it will carry in the air. Best angle (closest to 90)  10.  a) The acceleration is going down and east. b) 4.5 s to hit the ground. c) It lands 200 m away from the base of the cliff. 90m away from the bottom of the cliff

Physics Plus questions 1 and 2

Section 6
What do you see? - I see a kid in a chair with wheels leaning up next to a wall. Then the kid uses his legs to push off the wall and shoot off in the other direction. The air resistance causes the hat to fall of the dog and have the kid slow down.

What do you think? - I would tell that person to lean down, almost like sitting down in the air. The jult up as fast as possible trying to throw yourself as high as possible in the air. This will cause the person to jump.

Physics Talk - Newtons third law of motion is for every applied force, there is an equal and opposite force. The two forces always act on different objects. Inanimate objects can push back

Checking up questions 1. Describe Newton's first law of Motion - for every applied force, there is an equal and opposite force. The two forces always act on different objects. 2. Earth pulls down a mass with a force of gravity. What is the equal and opposite force acting in this situation? - The force pulling the object to the ground and making sure they do not move to the side. 3. What does a free-body diagram illustrate? - It shows the different forces that apply on an object. It is the gravity, friction, and normal.

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. 2. Acceleration is directly proportional to net force and inversely proportional to the mass of the system. 3. Every action an equal but opposite reaction.

Physics to Go 1. Yes it is true but it is opposite 2. No 3. There is a spring with a needle attached to it. 5. The mass of the linebacker will crush the running-back because he is much smaller than the linebacker. The smaller player has a bigger velocity 6. The speed of the hockey player. The mass of the player. It hits the board with a full speed. 7. The faster the ball is going the harder it will hit the glove. The impact will need to go straight into the glove. 8. The ice skater is skating really fast towards the puck and when they try to stop they crash into the boards. When they crash into the boards they hit it with a great momentum because of there speed and the mass. That causes the harder hit.

What do you think now? - I would tell them to try and lean down and use there legs to push off the ground as hard as they can. After pressing down you jolt up and bring your legs with you. Use this to carry your body into the air.

Section 7
What do you see? - I see a girl running on ice. It is easier to pull and run on the ice. On the sand it is harder for it to run because there is more friction.

What do you think? - When you play a certain sport you need different shoes because you need different traction for different sports. For instance, for golf you need shoes with spikes on the bottom so when you swing the club you do not slip and miss the ball. Another sport is track, because when you run on a track you need spikes on the bottom of you shoes because the shoes are so light and small that if you don't have spikes to grab onto the ground, you will slip, fall, and or not run as fast.

Physics to go 1. Football. The kicker would scrap his cleats in the ground to loosen up the turf so the kicker does not lose footing. 2. Snowboarding. A snowboarder would put wax on his board so he can move as fast as possible. 3. No because they would not be able to react as easily 4. They need more friction so they can move around as quick as possible. 5. It would be 18N. .03= f/600 = 18 6. If the speed limit was 65 mph he we be speeding. I will show work 7. The air and the water resistance need to depend on speed. When a water skier is gliding across the water the resistance stays the same but he moves faster. As you are falling like running through the water, the resistance is harder. 8. Yes it helps you move from point A to point B at a faster speed. The more friction the faster you can get going. The maximum strength the shoes can grip the ground. 10.If there is no friction than the runner will not be able to move. The friction allows the runner to move across the track.

Physics Talk Friction 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 ipposite in direction to the shoe's weight)

Coefficient of sliding friction: a dimensionless quantity; its value depends on the properties of the two surfaces in contact and is used to calculate the force of friction -the force of friction is = force required to slide the oject on the surface with a constant speed coefficient of sliding friction = F friction / F normal -no units bc it is a force divided by a force -expressed in decimals -valid only for the pair of surfaces in contact when the value is measure -if a surgace were tilted or if the pulling force were angled up/down, the force exerted by the surface on the object would be harder to determine

Checking up 1. The force of friction is equal to it because the pulling force that was applied to it was equal to the friction force. 2. The coefficient of sliding friction has no units because it is a force divided by another force 3. The force of friction is equal to force required to slide the object on that specific surface for constant speed.

Physics Plus #1



Part II: Friction and Kinematics Part III: Questions/ Conclusion 1. It is the amount of friction created between the brick and the floor. 2. They are very similar. 3. low 4. Yes. When you you need to know the friction between the shoes and the floor 5. - throwing speed - When the person is throwing it - The object can bounce when you throw it
 * Mass (g) || Mass (kg) || Measured Time (s) || Measured Distance (m) || Ff (N) || Acceleration (m/s2) || Calculated vi (m/s) || Calculated time (s) || % error ||
 * 170 || .17 || 2.05 || 9.37 || 3.3 || -2.7 || 7.11 || 2.2 || 6 ||
 * 170 || .17 || 1.57 || 5 || 3.3 || -2.7 || 5.19 || 2.2 || 40 ||
 * 170 || .17 || 1.83 || 7.3 || 3.3 || -2.7 || 6.28 || 2.2 || 16 ||

What do you think now? - The shoes need to be able to create more friction or less friction to allow that specific athlete to excel at his sport. - Different features for different shoes are useful for sports like basketball (you need a shoe that can stop and and go as fast as possible) and track (a shoes that has spikes on the bottom so you can grip the track better with more friction to allow you to get the longest stride to travel the greatest distance). Another example is for snowboarding (you need a board with a certain type of wax on the bottom so there is almost no friction between you and the board. The Less friction the faster you will go)

Section 8
What do you see? - There are people pole vaulting≥ He is trying to get to the party. The pole launches the body across the street up towards the party.

What do you think? - It is harder because the longer the pole the harder it is to carry and the more it will bend. You will need to be a heavier person to be able to do it. - The speed that they run at. The stability of the pole. The weight of the pole vaulter can cause them to go no where or really high.

Investigate Section 8

Prelab Activity: a. Hold one of the rulers ends on the table and while holding that you push down on the other end without breaking it and the farther the penny will travel b. How far the ruler is sticking out, How hard you push down on the end with the penny, How hard you push down on the end on the table, How high above the ground the ruler is, Where you place the penny.

Variable tested- Position of penny Methods and Materials- Apply the same pressure each time an move the penny

Data Table Conclusion: When the penny is at the end of the ruler the penny will travel the farthest.
 * end || middle || back ||
 * 70 cm || 20 cm || 2 cm ||

Types of Energy
 * Types of Energy || Definition || Equation and symbol ||
 * Kinetic Energy || energy something has because it is moving || KE = 1/2 mv2 ||
 * Gravitational Potential Energy || energy something has due to location relative to the ground (how high it is) || GPE = mgh

m- mass g- gravity ||
 * Elastic Potential Energy || energy a spring has when it is stretched or compressed || EPE = 1/2kx2

k- spring force constant ||


 * Work || caused when a force is exerted over some distance parallel to the motor || W = Fd ||

Physics to Go 1. You use kinetic in the begging and then at the end it goes to gravitational energy. W- GPE- W 2. When a golfer swings his club he is using kinetic energy and when it makes impact it doing work and then in the end it is using gravitational energy. SPE- W- KE-GPA-KE 3. 1/2mv2= mgh 1/2v2=gh 1/2(12)2= 100h h=7.2 4. The shorter and the harder it is to bend the bar, then the person will go higher. 5. The smaller and the harder it is to bend the bar, then the person will go higher. 6. I predict that it was around 4 mph to elevate her to that specific height. She has kinetic energy in the begining and at the end she has gravitational pull. 1/2m2 = mgh 1/2v2= (9.8)(4.55) = 9.44 7.  8. a) It will traveling at a speed of 20 mph. GPE= KE  mgh=1/2mv2  b) No you do not need to know because the masses cancel. 9. a) W= EPE =1/2kx2  = 1/2 (1500)(.25)  = 187.5  b) EPE=KE 1/2kx2=1/2mv2 = 1/2(1500)(.30) = 225  10. a) EPE=W  1/2kx2=fd  11. a) GPE = EPE mgh= 1/2kx2 b) Yes you need the mass. 12. F=ma  N kg m/s2  W= fd  J=Nm  GPE=mgh  = kgm/s2(m)  = J

Ke= 1/2mv2 =kgm/s2 =kgm/s2(m) = N(m) =J

EPE=1/2 kx2 =J

13. 14. THe volleyball placer is using work. She is pushing the ball and then when it leaves her hands it goes through kinetic (KE) and then it finally goes to gravitational(GPE). 15. 16.

What do you think now? - It is because if you are running at the same speed then it will not matter. You need to have a greater speed of the pole. You need it to be stretchy but not too stretchy that it will break. The amount of kinetic energy put in is the amount of gravitational energy put out.

Section 9
What do you see? - There is a ice skater skating and then she jumps. There is a person with a stopwatch seeing how long her hang time is. Hang time is the amount of time something is in the air for.

What do you think? - Do athletes defy the laws of gravity- No they ca't because they would not be a law then. - Does a skater stay in the air long enough to do a triple axel- No they don't because if they stayed in the air any longer then you will be defying gravity. WHich is not possible.

Investigate Section 9

Prelab activity Skater 2. The skater is in the air for 20 frames which is 1/30 which equals 2/3 second. 3. 2/3 second 4. Yes because the skater is in a straight line for a good period of time. It is 8 frames in that when he is hovering and it goes to 9 until her starts falling.

Basketball player 2. The basketball player is in the air for 31 frames. 3. 31/30 which is about 1 second 4. No because he was at a more vertical angle than the skater so he reached a point and then started to go down.

Instructions 1. first- bend your knees to get as low to the ground as possible whithout sitting on the ground. STAGE A ( Work due to unbending) second- you are unbending your knees jolting oneself into the air. STAGE B third- you go airborne ( GPE )

W (unbending legs) = GPE (final)

2. a) You will be able to find the force that is needed to get into the air.  b) I will record the height of my jump, my height, how far I bend my knees, and how much my specific weight is. c) I will use the ruler to get my specific height of the jump. d) Using data studio e) W= GPE fd= mgh  f(.1)= (70.3)(9.8)(.29)  f = 1,997 N  Measurements: 1,908 N : My calculation is a little bit higher because there is some careless errors that my have occurred during the calculation of the height of my jump.  ﻿%error=I calc-expI/calc (100)  = 1997-1908= 89  89/1997 = .04456685  .04456685(100) = 4.45 %  My percent error was 4.45%

Physics to go 1. W = GPE = mgh = (50)(9.8)(1) = 490 J  2. W + GPE --> KE + W  3. No there is not hang time because if you put it into separate time segments, and it was not at one point the same height. It was all different. 4. Yes because they need to be able to prove that it is wrong. There is evidence that shows that it is true so you have to show that it is not true. 5. YOu put work in and then you get height W = GPE fd = mgh increase your force or you can decrease your mass 6. w = fd a) 1 J  b) 10 c) 10 J d) 10 J  c) 10 J  7. W = GPE  1 J = 1 J  8. W =fd  1 J  10 J  9.  = fd  = (50)(4.3)  = 215 J  10. ke = 1/2mv2  11. a = F/m  = 30/5  = 6  b) 563 12. d = w/f 12.5 m 2.7 m/s2 13. W = fd 1/mv2 = 120 14. W = Ke  fd = 1/2mv2 = 17 m 15.
 * || Ke || GPE || EPE || Jules ||
 * running || 100J || 0 || 0 || 1000 ||
 * Full bend || 100 || 0 || 900 || 1000 ||
 * || 0 || 1000 || 0 || 1000 ||
 * landing || 850 || 150 || 0 || 1000 ||
 * cushion || 0 || 0 || 0 || 0 ||

16.
 * || Ke || GPE || EPE || Jules ||
 * Peak || 0 || 1000 || 0 || 1000 ||
 * landing || 800 || 200 || 0 || 1000 ||
 * Compress || 0 || 0 || 1000 || 1000 ||

17.
 * || KE || GPE || EPE || Jules ||
 * top || 0 || 1000 || 0 || 1000 ||
 * middle || 100 || 500 || 0 || 1000 ||
 * bottom || 1000 || 0 || 0 || 1000 ||

Physics Plus

1. a) KE = GPE  1/2mv2 = mgh  1/2v2 = gh  1/2v2 = (9.8)(20)  v = 19.8  b) So that it is all based on the height of the ride. If the ride is equal height that it will be able to travel the entire time without stopping.

2. EPE = KE  1/2kx2 = 1/2mv2 1/2(60)(.16) = 1/2(.3)v2 x =5.66

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

What do you think now? - They can do the triple axel, but they are not defying gravity because they are going to travel upwards until they reach a max height. Once the max height is reached then they start to go down. The skater is doing work to get into the air and then gravitational potential is taking over which allows that skater to stay in the air for a certain period of time.