Physics Study Packet

Physics Study Packet E

spring = ½ kx

Work = F * d V = AR P = VA Gravitational PE = mgh F* change in t = m * change in v E

before = E after

EK = ( ½ )mv2 J = N*m Amps = the amount of electricity flowing past a point in one second. NET

momentum before = NET momentum after

Speed = d/t COR (V 1b – V 2b) = - (V 1a – V 2a) Pb = Pa By Anna Brodski

1. Walking down the street one day, you smack a street sign with your hand. It vibrates with a frequency of 6 Hz. This intrigues you and you decided that you want to vibrate the sign a greater distance. What should you do and why will this work?

a. A Car is moving at 20 m/s. How far does the car go in 20 s?

b. How far does the car go in 5 minutes?

2. The shot put is a competition to throw a heavy weight as far as possible. The best technique involves people throwing the shot while running. Why does this cause the shot to go farther?

3. a. Does a lens Bend light rays? How do you know?

b. Say the lens was placed into a fluid with the same index of refraction as the lens. Would the lens still make an image? Defend your answer.

4. A lens is used to make a clear image of an apple. Then the letter J is written on it in opaque black marker. A person then tries to make an image using this written on lens. How will the image be different, if at all, over the original image? Be sure to defend your answer using a successful model.

5. a. A magnifying glass can be used to burn paper or other materials by making an image of the sun. Using a successful model, explain why this works. Make sure that you give a complete explanation.

b. A pinhole can also be used to make an image of the sun. Can you use the image made by the pinhole to burn paper? Using a successful model, explain why this works. Make sure that you give a complete explanation.

7. A car has gone a distance of 120 mi. If it has gone that distance in (a) 1 hr, its speed is

(b) 2 hr, its speed is

(c) 3 hr, its speed is

(d) 6 hr, its speed is

(e) 5.5 hr, its speed is

8. A car is moving at 30 mi/hr. How far has the car gone in (a) 1 hour?

(b) 2 hours?

(c) 3 hours?

(d) 0.5 (one-half) hour?

(e) 3.5 hours?

9. A stream has water flowing in it at 9 km/h with respect to the shore. Call the direction that the water is flowing positive. (a) A boat is traveling downstream (in the same direction as the water) at 10 km/h. How fast is the boat moving compared to the shore?

(b) A child on the same boat walks from the front to the rear of the boat (opposite the direction of the water) at 7 km/h. How fast is the child moving compared to the shore?

(c) The boat then turns around and travels upstream (opposite the direction of the water). How fast is the boat now moving compared to the shore?

10. Superman must rescue a pair of trains. Train A is moving west down a track at 55 km/h. Train B is moving east down the same track at 100 km/h. If the trains are 50 km apart, how long in hours does Superman have before the trains collide?

11. A football quarterback is at rest when he is tackled by a linebacker who is moving at 10 m/s and masses 114kg. After the collision the two players get tangled together and move at 6 m/s. How massive is the quarterback?

12. (a) What is the momentum of an 7 kg bowling ball rolling at 5 m/s? (b) The bowling ball hits a pin that masses 1.5 kg, and the pin goes flying off at 10 m/s. How fast is the bowling bowl moving after the collision?

13. A 34 kg canoe is at rest with respect to a pier. A 54 kg kid is a rest with respect to the canoe. (a) She starts walking forward (call that the positive direction) in the canoe at 2 m/s with respect to the pier. How fast does the canoe start moving with respect to the pier? (b) How fast is she moving with respect to the canoe? (c) Realizing that she is moving away from the pier, she stops moving with respect to the canoe. What is now the canoe's speed with respect to the pier?

14. A 5 kg blob of putty moving at 2 m/s slams into a 2 kg blob of putty at rest. (a) Calculate the speed of the two stuck together blobs of putty immediately after colliding. (b) Calculate the speed of the two blobs if the one at rest was 4 kg.

15. A 3 kg fish swimming 5 m/s swallows an absent minded 1 kg fish at rest, as shown below. (a) What is the speed of the large fish immediately after lunch?

(b) What would its speed be if the small fish were swimming towards it at 4 m/s?

16 .A 50 gram pool ball is moving at 6 m/s when it hits another pool ball (also 50 grams) that is at rest. If the first ball stops after the collision, how fast is the second ball moving after the collision?

17. A 60 kg girl is serving a 250 g volleyball. She tosses the ball upwards and hits the ball when it is at rest by her 9 kg hand and arm at 18 m/s. If her arm is moving at 17 m/s after the collision, how fast is the ball moving after the collision? (Assume that the direction the hand was originally moving is positive.)

18. A 145 gram baseball is moving at 40 m/s towards a 1.1 kg baseball bat moving at 16 m/s in the opposite direction of the ball. If the bat is moving at 8 m/s after the collision, how fast is the ball moving after the collision? (Call the direction that the ball was originally moving positive.)

19. A 40 gram ball is moving at -20 m/s when it hits a 1.5 kg raquet that is moving at 14 m/s in the opposite direction. (a) After the collision, the racquet is moving at 12 m/s in the same direction as before. If the ball is moving at 30 m/s after the collision, what is the coefficient of restitution? (b) What is the momentum before the collision? (c) What is the momentum after the collision? (No Response) (d) Is it possible that this a real collision?

20. A golf club masses 200 grams and is moving at 33 m/s when it hits a 50 gram golf ball at rest. Assume that the collision is perfectly elastic and so the coefficient of restitution is 1.00. (a) How fast is the club going after the collision? (b) How fast is the ball moving after the collision? (c) Real golf clubs are not allowed to have a coefficient of restitution greater than 0.83. Will the speed of the golf ball be greater or smaller after the collision with the smaller coefficient of restitution? (d) With the lower COR, will the club be moving faster or slower after the collision than it did with a COR of 1? (e) How fast is the club going after the new collision? (f) How fast is the ball moving after the new collision?

21.A golf ball of mass 0.045 kg is hit off the tee at a speed of 43 m/s in the positive direction. The golf club was in contact with the ball for 0.050s (a) Find the change in momentum imparted to the golf ball. (The units for momentum are kg m/s.)

(b) Find the force exerted on the ball by the golf club.

22.A person is riding a bicycle. (a) A person masses 61 kg. She can apply a force of 100 N with their legs. How fast will she be going after 1 s? (b) How fast will she be going after 2 s? (c) How fast will she be going after 3 s?

23.A person is riding a bicycle. (a) A person masses 57 kg. After 3 s, how fast will he be going if he can apply 100 N of force? (b) How fast will she be going after 200 N of force?

24.A softball that masses 0.2 kg is moving at 25 m/s (call this positive) towards a bat that masses 1.9 kg and is moving at 17 m/s in the opposite direction. After the collision the bat is moving at 11 m/s. How fast is the ball moving after the collision?

25.All of these questions take place on the surface of the earth. (a) What is the force of gravity on Amy who is 55 kg? (b) What is the force of gravity on Bob who is 58 kg? (c) What is the force of gravity on Cecil who is 61 kg? (d) What is the force of gravity on Darla who is 70 kg? (e) What is the force of gravity on Erasmus who is 72 kg? (f) What is the force of gravity on Felicia who is 83 kg?

26. (a) What impulse occurs when an average force of 7 N is exerted on a cart for 1.6 s? (b) What change in momentum does the cart undergo? (c) If the mass of the cart is 2 kg and the cart is initially at rest, calculate its final speed.

27. Assume that positive is in the direction that the ball is rolling. (a) What is the momentum of an 7 kg bowling ball rolling at 3 m/s? (b) If the bowling ball rolls into a pillow and stops in 0.5 s, calculate the average force it exerts on the pillow. (c) What average force does the pillow exert on the ball?

28.Assume that positive is in the direction of the motion of the box. (a) What is the momentum of a 40 kg carton that slides at 1 m/s across an icy surface? (b) The sliding carton skids onto a rough surface and stops in 3 s. Calculate the force of friction it encounters.

29. Assume a 10 kg bowling ball moving at 2 m/s bounces off a spring at the same speed that it had before bouncing. Positive is the direction of the initial roll of the ball. (a) What is its momentum of recoil?

(b) What is its change in momentum? (Hint: What is the change in temperature when something goes from 1 degree to -1 degree?) (c) If the interaction with the spring occurs in 0.5 s, calculate the average force the spring exerts on it.

30. How does the change in velocity of the cannon compare with that of the cannonball? Defend your answer.

31. If you hit a wall with a force of 280 N, how much force is exerted on you?

32. A 3kg Pendulum that is attached to the ceiling is pulled up to a height of 1.8 m from the floor. It is then released while also giving it a push of 3m/s, swinging down to a lowest point of 0.2 m off the floor. It swings to the other side and then swings back. (a) Explain why it might decapitate the person.

(b) How fast is the bob moving at its lowest point?

(c) If the person dodges out of the way how high will the bob go?

(d) What if the person doesn’t dodge? If the bob were to come to a stop against the person’s face in 0.3 seconds, how much force would the bob apply to the face?

33. A dart gun has a spring constant of 500 N/m. A 15 gram (0.015 kg) dart is placed in the spring has been compressed 0.1 m.

(b) If the dart gun is turned horizontally, how fast will the dart be moving when it leaves the gun?

(c) If the dart experiences 1.2 N of friction over the 10 cm it moves in the barrel how fast will it be going when it leaves the gun?

34. A 3000 kg car has an engine that can apply a force of 9000 N to the road. (a) How much work does the car do if it is applying the force for 150 m?

(b) Assuming no friction and it is starting from rest, how fast is the car moving after 150 m?

(c) How much time will that take?

35. A 2000 kg car has wheels that can apply a maximum of 10,000 N of force to the ground before they start to slide. If the car is going around a curve that is 50 m in radius, what is the fastest that the car can go and stay on the curve?

36. Along the highway, you might see a runaway truck ramp. It is for trucks whose brakes have gotten so hot that they are in danger of failing because of overheating. (a) Why are trucks more in danger of this than cars? (Cars are still in danger, but less so.)

(b) Runaway truck ramps are most often found along roads that are going down long hills. Why is that?

(c) Runaway truck ramps are often covered in gravel, rocks and sand. Why might that be helpful in stopping the truck?

37. (a) A tennis racquet (300 grams) is moving at 10 m/s when it hits a tennis ball ( mass 80 grams) that is moving at 30 m/s the other way. The ball bounces off the racquet moving at 40 m/s in the direction that the racquet is moving. How fast is the racquet moving now?

(c) In terms of what we have studied this year, is this collision possible? Defend your answer.

38. Can the screen be placed anywhere to make an image, or does it need to be in a particular place with respect to the lens and bulb? Defend your answer.

39. Light is constantly streaming out of the fluorescent bulbs overhead. Why cant you see the light flowing out of the bulbs? Of course, you can see that objects are lit by the lights, but you can’t see the light itself. Why not?

(b) Why cant you see around a corner?

(c) Well, you can see around a corner with a mirror. So what do you think that a mirror does? Describe an experiment that would allow you to test your idea.

40. When you use a magnifying glass to look closely at an object, is what you see through the class inverted? Do you think that looking through a magnifying glass is the same as making an image like we are doing here? Defend your reasoning.

(b) A camera uses a lens to make an image. Is the image in the camera inverted?

41. Most higher quality cameras have lenses that move back and forth compared to where the film lies. Does the lens need to be a certain distance away from the film? What will happen if the lens is in the wrong spot? (some cameras have a zoom feature that changes the size of the image; that part works differently. Don’t worry about that now.)

(b) What do you think the lens is doing to the rays of light that are coming out of the filament? Does it change their direction? How do you know this? Does your model explain what happens if the lens isn’t in the right place? Keep reworking yiur model until it gives an adequate explanation.

42. Many light bulbs contain filaments. Should you see images of the filaments everywhere? Why or why not?

(b) What do you think a lens does for camera? Would the camera work without the lens? What would appear on the film if there were no lens?

43. Does light from every part of the filament fo through every part of the lens? How do you know?

(b) Inside of your eye, between the lens and the retina where the image is, are bits of material called floaters. These floaters can rarely be seen. Why? If they get really close to the retina, you can see it. Why?

44. Does an object need to be luminous (glowing) for it to make an image?

(b) How might a artist use these ideas to aid in drawing?

45. A camera works in much the same way that the magnifying glasses in class do. What does the lens have to do to make the image on the film sharp? Why does this work? Use your model.

(b) According to your model, do the lines of the filament get less bright if you move the screen a small amount?

46. When the sun is shining brightly, you can see spots of light underneath trees. What do you think these spots are?

47. Does the pinhole bend the rays? What does the pinhole do?

(b) Where does the image get flipped over, or does the question not make any sense?

48. Some cameras don’t have lenses. Instead they have small holes. Why does this work, and what are the limitations?

49. Your eyes pupil works like a pinhole, so why does your eye need a lens as well?

50. An apple, a lens, and a screen are placed in such a way as to get a clear image of the apple on the screen. A pinhole is then placed directly in front of the lens. What will happen, if anything, to the image on the screen? Defend your answer.

51. Children have used magnifying glasses to start small fires. (A) explain what is happening when a magnifying glass is used to start a fire.

(b) Why does a larger magnifying glass make a hotter fire?

(c) Can a pinhole be used to start a fire? Why or why not?

52. (a) You hear a person singing. Is something vibrating inside them? How do you know?

(b) Many people who are profoundly deaf can still tell when music is being played. How do you think they do it?

53. How do you tell by touch whether a sound is high or low pitched?

54. The buzz of mosquito is very high pitched. What does that say about how fast its wings are moving?

(b) Some stereo speakers have two parts: a woofer that plays low pitched sounds and a tweeter that plays high pitched sounds. The tweeter often looks like it isn’t doing anything. What’s up with that?

55. Sometimes a stereo can be played so loudly that it breaks. What is going on that is breaks?

(b) How do you pluck a guitar string to make it louder? How do you know this.

56. The movie Alien had the tag line, “In space no one can hear you scream.” Explain.

(b) What if instead of there being no medium, the medium cannot move. Would sound still be able to get through?

57. Is a wave a thing?

(b) If a person is saying something you don’t like. Can you stop the waves by yelling back?

(c) Why does singing while someone else is talking make him or her hard to understand?

58. There are these cool headphones that when you turn them on, everything us quieter rather than louder. How do you think that these work? A slight defect will make them work in reverse. What is the defect and why does it make everything louder instead of quieter?

(b) At a dance, sometimes near a well you will find a spot where the sound of the bass is especially loud, but a few steps away, the sound is quieter. What is going on? Don’t just answer interference; explain what is going on.

59. Use your model to show how lens can make an image on a screen of something that is half red and half blue.

(b) Say you move the screen forward so that the image is badly out of focus. Use your model to figure out what color the blurry image will be..

60. The speed of compressions and expansions in sound waves is always with respect to the air not the ground or the people doing the moving. (a) How do you think that a sound would be different if its waves always moved with respect to the ground?

(b) Does being in the wind change the pitch of a sound?

61. We have discussed that sound is in some sense just a series of collisions. In particular we can imagine them to be elastic collisions with a coefficient of restitution of 1. (a) So lets do a problem where an air molecule of mass 1 (units, who needs stickin’ units?) that is moving at 200 m/s hits another air molecule initially at rest that also has a mass of 1. how fast are both moving after the collision? (Now sound works differently than this, but this isn’t a terrible model).

(b) Describe Where the momentum from the first molecule went?

(c) Repeat but this time the air molecule hits a glass molecule that has a mass of 20 that is at rest.

(d) Where did the momentum go in this case? Who had more momentum after the collision?

(e) Repeat again, but this time it is 200 m/s glass molecule hitting a still air molecule.

62. (a) Why are the strings on a piano that are designed for low pitches have dense copper wire wrapped around them?

63. (a) To play a higher note on a guitar, do you want to make the guitar string stiffer or less stiff or will it not matter? Why?

(b) What happens to the stiffness of your vocal chords when you say a lower pitched note? How do you know?

64. (a) Whap happens to the loudness of guitar strings if you pull the strings down more?

(b) What happens to the pitch of the guitar strings if you pull the string down more?

65. (a) If a guitar string is stretched and then realeased, what will happen to the string afterwards?

(b) Does everything have a natural frequency?

66. (a) A clock will make a ticking noise, but when it is placed on a hard table it will often be louder. Why?

(b) A harp is generally much quieter than a piano even though they are both string instruments. Why?

67. Object A is moving (compared to the ground) along and hits object B which was originally not moving (compared to the ground). Object B then starts to move. (a) Do you think that B gained momentum? You may want to define momentum in your answer.

68. (a) Does Lens bend light rays? How do you know?

(b) Say a lens was placed into a fluid with the same index of refraction as the lens. Would the lens still make an image? Defend your answer.

69. A lens is used to make a clear image of an apple. Then, the less “J” is written on it in opaque black marker. A person then tries to make an image using this written on lens. How will the image be different, if at all, over the original image? Be sure to defend your answer using a successful model.

70. The letters “JCHS” are written vertically in front of a pinhole. An opaque card is placed behind the pinhole as shown in the picture above. What will appear on the screen? Be as specific as you can. Sketch what will appear. Support your answer with a successful model.

71. The shot put is a competition to throw a heavy weight as far as possible. The best technique involves people throwing the shot put while running, Why does this cause the shot to go farther?

72. (a) A car is moving at 20m/s. How far does the car go in 20 s?

73. In the high jump, a person tries to jump over a bar. It turns out that it is not an advantage to run towards the bar, a little jog is all that is needed with a hard straight up jump just before the bar. Explain in terms of physics that we have learned so far this semester why this works.

74. (a) A marathon is 42, 195 m. The faster time for a man to complete a marathon is 7,466 s. (2hrs, 4min, 26 s) What is his speed?

(b) Assuming that he goes the same speed the entire race, how long would it take him to run 1600m? (1600 m is about a mile.)

75. A golf club (1kg) that is moving at 20 m/s hits a golf ball (0.046 kg) that is at rest. After the collision, the golf ball is moving at 60 m/s. If the collision takes 0.02 sec, how much force was exerted on the golf ball?

(b) What was the ball’s change in momentum?

76. when a sound compression or rarefaction hits a wall it can reflect backwards (that is, it can echo). An echo of a clap doesn’t make a pitch – it still sounds like a single compression. Strangely, if it is hitting a stepped surface like in the picture above, the reflected sounds can make a distinguishable pitch. (a) explain.

(b) In the second picture, the steps are closer together. Will the pitch be higher, lower or the same in the second situation? Defend your answer.

77. Inside your inner ear, you have a long membrane called the basal membrane. It starts narrow and gets wider. When you hear a sound, your eardrum forces several bones to vibrate which eventually force the basal membrane to vibrate. Different part of the basal membrane start to vibrate when your hear different pitches. Nerves next to the membrane detect the vibration in the place and send the information to your brain. (a) Which part of the membrane will vibrate when you hear a low pitch? Defend your answer.

(b) If you hear a really loud sound it can damage the nerves. Explain how that might occur.

78. (a) A person is inside of a car moving at a constant speed. They throw a ball in the air so that they can catch it, Should they throw the ball forward or backwards or straight up? Defend your answer.

(b) The person tries this again another day, but the car has a sunroof and the ball goes out it. For some reason, the ball doesn’t come back down to the person’s hand. Explain in terms that we have studied for this unit why the ball doesn’t come back this time.

79. The earth is moving at 1000 mi/hr or 440 m/s. If you jump straight up into the air for 0.5 s, how far has the earth turner in that time?

(b) How come you don’t hurt yourself if you are in a small room?

80. Police often measure the speed of a car by drawing two lines on a road a certain distance apart and then measuring the time the car takes to go between the two lines. If two lines are 200 m apart and a car takes 5 s, to cross the lines, how fast is the car moving?

(b) Of course, the police want the speed in mi/hr. Please convert. (hint: There are about 1600 m in a mile.)

81. A speaker is mounted on top of a toy car as shown above, The speaker is turned on to a very loud setting. Will the speaker be able to drive the car to the left? To the right? Will the car move at all? If so explain how the car will move. Defend your answer. Be sure to use information that you have learned this year.

82. In general, a larger lens will make a brighter image than a smaller lens. Explain why this is true.

83. A marimba is a musical instrument. A marimba has a series of wooden bars of different lengths. It is played by hitting a small mallet at the bottom against one of the bars. (a) Is this an example of natural frequency, forced vibration, resonance or none of these? Explain your answer.

(b)Marimba’s are not very loud. To make them louder, they add hollow tubes under the bars. Why does this make them louder? (hint the face that the tubes are different lengths is important.)

84. A wind chime is a series of tubes suspended from a frame with a clapper that hits them when the wind blows. (a) Longer tubes make lower pitched sounds than shorter tubes. Why is this the case?

(b) The tubes on most wind chimes are made of steel, but some are made of opper which is less stiff than steel. For two tubes the same length, which will have a lower pitch or will they be the same? Explain your answer.

85. (a) A magnifying glass can be used to burn paper or other materials by making an image of the sun. Using a successful model, explain why this works. Make sure that you give a complete explanation.

(b) A pinhole can also be used to make an image of the sun. Can you use the image made by a pinhole to burn paper? Using a successful model, explain why this works. Make sure that you give a complete explanation.

86. Earthquakes consist of waves (sort of like giant, low frequency sound waves) that can shake buildings apart. To protect buildings from these waves, some buildings have giand balls placed inside of them on huge motors. The motors can shake the balls back and forth. Explain how this protects the building from earthquakes and how the motors need to move the ball from this to work.

87. Car A is moving at 20 mi/h and is 2 miles in front of Car B. Car B is moving at 24 mi/h. How long will it take car B to pass Car A?

88. A car tire has a rock stuck to one side. Each time the wheel goes around it seems to make a click. As the car gets faster, does the pitch generated by the rotating wheel change? (Does it make a pitch at all?) Does the loudness of the click change?

89. (a) A music box is much louder when it is placed against a table top rather than vibrated in air. Why?

(b) Does the music box vibrate the table at the table’s natural frequency? How can you tell?

90. In the moves when people pull the cords to open their parachutes they seem to fly upwards. I’ve been parachuting and that just doesn’t happen. Instead opening your parachute just slows you down explain in terms of what we have covered in this unit, why is appears that people fly upwards when they open their parachutes. Hint: Someone has to film what is going on.

91. (a) A 60 kg person is standing on a scale on the surface of the earth. What is the force of gravity between him and the earth?

(c) The person then jumps upwards with a force of 1000 N for 0.4 s. How fast do they leave the ground?

© An electric car can go from 0 to 60 mi/hr in 10 sec on earth. When the car is sent to the moon, how fast will it be able to go from 0 to 60 mi/hr? (don’t worry about the fact that the moon doesn’t have any air, the car still runs fine there. The road on the moon is smooth and level.) Explain your reasoning.

92. Natalie (m – 50 kg, height = 160 cm) and Jill (m = 70 kg, height = 180 cm) are standing on roller blades (assume that friction plays a very small role). (a) Natalie rugs on Jill with a force of 40 N for 3 s. How fast will jull be moving after that time?

(b) Will Natalie start moving? If so calculate how fast Natalie will be moving after 3 s? If not, explain why Natalie wont start moving.

(b) How far does the same car go in 5 minutes?

73. Walking down the street one day, you smack a street sign with your hand. It vibrates with a frequency of 6 Hz. This intrigues you and you decided that you want to vibrate the sign a greater distance. What should you do ad why will this work?

.