Physics Test 2 Ch 6,7, 11, 19, 20

25. What will be the kinetic energy of a pile driver ram starting from rest that undergoes a 10-kJ decrease in potential energy?

10 kJ

36. What is the efficiency of a machine that miraculously converts all the input energy to useful output energy?

100%

3. A force of 50 N is applied to the end of a lever, which is moved a certain distance. If the other end of the lever moves one-third as far, how much force does it exert?

150 N

42. If you push a crate horizontally with 100 N across a 10-m factory floor and friction between the crate and the floor is a steady 70 N, how much kinetic energy is gained by the crate?

300 J

40. What beat frequency will occur when a 370-Hz and a 374-Hz sound source are sounded together?

4 Hz

5. In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m?

50 J

64. When the useful energy output of a simple machine is 100 J, and the total energy input is 200 J, the efficiency is _______.

50 percent

70. If an input of 100 J in a pulley system increases the potential energy of a load by 60 J, what is the efficiency of the system?

60%

53. How many periods are in the periodic table? How many groups?

7 periods and 18 groups

4. Shown above right are four different pairs of transverse wave pulses that move toward each other. At some point in time, the pulses meet and interact (interfere) with each other. Rank the four cases, from most to least, on the basis of the amplitude of the peak that results when the centers of the pulses coincide.

A B D C

46. In the preceding question, which case requires the greatest impulse?

A baseball that is caught and then thrown back

8. Can a machine multiply input force? Input distance? Input energy?

A machine can multiply input force. A machine can multiply input distance. A machine cannot multiply input energy.

31. What is the meaning of the term nucleon?

A proton or neutron

35. Give an example in which a force is exerted on an object without doing work on the object.

A satellite is in a circular orbit about Earth.

1. A bow wave on the surface of water is two-dimensional. What about a shock wave in air?

A shock wave in air is three-dimensional.

63. Rank the scale readings from most to least. (Ignore friction.)

A, C/B

38. What is meant by a blue shift and a red shift for light?

An approaching source has increased light frequency - a blue shift. A receding source has a decreasing frequency - a red shift.

28. How does the speed of sound in water affect refraction under water?

As different layers of water have different temperatures, the speed of sound varies, and refraction occurs.

57. Are standing waves a property of transverse waves, of longitudinal waves, or of both?

Both

30. Which requires more work--lifting a 50-kg sack vertically 2 m or lifting a 25-kg sack vertically 4 m?

Both take the same 1000 J

34. A hungry fish is about to have lunch at the speeds shown below. Assume the hungry fish has a mass 5 times that of the small fish. Immediately after lunch, rank the speed of the formerly hungry fish from each case from greatest to least.

C: v= 2m/s v= 3m/s B: v= 3m/s v = 9m/s A: v = 2m/s 5m/s

45. If a machine multiplies force by a factor of 4, what other quantity is diminished, and by how much?

Distance is diminished to one-quarter.

47. Which of the following are negatively charged?

Electrons

7. Is it momentum or energy that enables an object to do work?

Energy

74. To increase the momentum of an object, should you exert a large force, or extend that force for as long a time as possible--or both? Explain.

Exert a large force over the longest time because momentum is proportional to both force and time.

23. Lil drives her car with a mass of 1000 kg at a speed of 18 m/s What is the magnitude of road friction force that is needed to bring her car to a halt in 5.0 s?

F = 3600 N

18. Nellie Newton applies a force of 54 N to the end of a lever, which is moved a certain distance. If the other end of the lever moves one-third as far, find the force it can exert.

F= 160 N

60. True or false: In order for an object to produce a sonic boom, it must be "noisy." Give two examples to support your answer.

False. A whip and a bullet move through the air without making sounds other than the shock wave.

32. True or false: A sonic boom occurs only when an aircraft is breaking through the sound barrier. Defend your answer.

False. An aircraft creates a shock wave continuously as it is supersonic. This is heard as a sonic boom by an observer.

6. Does sound travel faster in warm air or in cold air? In humid air or dry air?

Faster in warm air, faster in humid air

78. How much impulse stops a 40-kg carton sliding at 5.2 m/s when it meets a rough surface?

I = 210 N⋅s

61. Impulse = change in momentum: Ft=Δmv What is the impulse on a 7.5-kg ball rolling at 2.8 m/s when it bumps into a basket and stops?

I =21 N⋅s

39. Distinguish between a compression and a rarefaction.

In a compression, the molecules are closer together than average; in a rarefaction, they are further apart.

67. What factors does the speed of sound depend upon? What are some factors that it does not depend upon?

It depends on temperature and humidity, not on loudness and frequency.

56. How does the electric charge of an electron compare with the electric charge of a proton?

It is equal and opposite.

24. A sack is raised a certain distance in a construction site and therefore has potential energy relative to the ground below. If it were raised twice as high, how much more potential energy would it have?

It would have twice as much potential energy.

76. In which type or kind of collision is momentum conserved: elastic or inelastic?

Momentum is conserved in elastic and inelastic collisions.

51. How does elasticity relate to an object's natural frequency?

Natural frequency increases with increasing elasticity of the object.

17. Which energy production method does not ultimately depend on the Sun?

Nuclear fission

27. Where did the heaviest elements originate?

Nuclear fusion in supernovae

55. Which baseball undergoes the greatest change in momentum at the same speed immediately after being caught and being thrown?

One that is caught and then thrown back.

13. In the Doppler effect, does frequency change? Does wave speed change?

Only frequency changes.

20. Select the correct equations that show that 1000 W of power is expended when a 500-N crate is lifted 4.0 m above the floor in 2.0 s

P=W/t=Fd/t=(500N)(4.0m)/(2.0s)=1000W

72. A ball is released from rest at the left of the metal track shown below. Assume it has only enough friction to roll, but not to lessen its speed. Part A: Rank momentum from greatest to least at each point. Part B: Part C:

Part A: (C, B/D, A) Part B: (C, B/D, A) Part C: (A, B/D, C)

37. The mass and speed of the three vehicles, A, B, and C, are shown A. 1.0 m/s 800kg B. 2.0 m/s 1000kg C. 8.0 m/s 90kg Part A: Rank from greatest to least their momentum. Part B: Rank from greatest to least their kinetic energy. Part C: Rank from greatest to least their work needed to bring them up to their respective speeds from rest.

Part A: BAC Part B: CBA Part C: CBA

75. All the waves shown have the same speed in the same medium. Part A: Use a ruler and rank these waves from most to least for amplitude. Part B: Use a ruler and rank these waves from most to least for wavelength. Part C: Use a ruler and rank these waves from most to least for frequency. Part D: Use a ruler and rank these waves from most to least for period.

Part A: D,B,A,C Part B: D,A,B,C Part C: C,B,A,D Part D: D,A,B,C

21. Part A: How much work is done when you push a crate horizontally with 150 N across a 7.0-m factory floor? Part B: If the force of friction on the crate is a steady 70 N, find the KE gained by the crate. Part C: Find the "missing energy".

Part A: W = 1100 J Part B: K = 560 J Part C: Q = 490 J

33. Part A: A railroad locomotive is at rest with its whistle shrieking, then starts moving toward you. Does the frequency of sound that you hear increase, decrease, or stay the same? Part B: How about the wavelength reaching your ear? Part C: How about the speed of sound in the air between you and the locomotive?

Part A: increases Part B: decreases Part C: stays the same

48. How does speed generally affect the amount of friction between a road and a skidding tire?

Speed has no effect on the friction.

26. Why does sound tend to bend as it grazes warm ground?

Speed of sound increases in the warmed air, so sound refracts upward.

12. Which is normally greater, the energy in ordinary sound or the energy in ordinary light? How does the speed of sound compare to the speed of light?

The energy in ordinary light is greater than the energy in ordinary sound. The speed of sound is a million times less than the speed of light.

69. If two sacks, one twice as heavy as the other, are lifted the same vertical distances in the same time, how does the power required for each compare?

The heavier sack requires twice the power.

79. Rank the periods of a clock from largest to smallest.

The hour hand The minute hand The second hand

68. Why are heavier elements not much larger than lighter elements?

The larger positive charge in the nucleus pulls the electrons into closer orbits.

62. Why when tuning a radio do you hear only one station at a time rather than hearing many stations at once?

The natural frequency of the electronics is tuned to resonate with the frequency of one station.

50. Compared with the energy it takes to separate oxygen and hydrogen from water, how much energy is released when they recombine? (Think conservation of energy.)

The same amount of energy is released when they recombine.

9. Rolling railroad car A makes a perfectly elastic collision with railroad car B of the same mass. After the collision, car A is at rest. How does the speed of car B compare with the initial speed of car A?

The speed of car B is equal to the initial speed of car A.

2. Why will a struck tuning fork sound louder when it is held against a table?

The table is forced to vibrate, and its large surface vibrates more air than the tuning fork.

11. If the equally massive railroad cars A and B stick together after an inelastic collision, how does their speed after the collision compare with the initial speed of car A?

Their speed is half the initial speed of car A.

52. What is the source of energy in sunshine?

Thermonuclear fusion energy

65. What occurs when a proton and an antiproton meet?

They annihilate each other.

77. In the hydraulic machine shown below, when the small piston is pushed down 10 cm, the large piston is raised 1 cm If the small piston is pushed down with a force of 100 N, what is the most weight that the large piston can support?

W = 1000 N

41. How do forced vibrations relate to resonance?

When forced vibrations match an object's natural frequency, resonant amplification occurs.

10. How do matter and antimatter differ?

When matter and antimatter meet, they annihilate in a flash of energy.

49. A force sets an object in motion. When the force is multiplied by the time of its application, we call the quantity impulse, which changes the momentum of that object. What do we call the quantity force multiplied by distance?

Work

44. You watch distant Sally Homemaker driving nails into a front porch at a regular rate of 1 stroke per second. You hear the sound of the blows exactly synchronized with the blows you see. And then you hear one more blow after you see the hammering stop. Calculate the distance of Sally from you.

d = 340 m

19. Imagine a Rip van Winkle type who lives in the mountains. Just before going to sleep, he yells, "WAKE UP", and the sound echoes off the nearest mountain and returns 7.8 hours later. Find the distance between Rip and the imaginary mountain.

d = 4800 km

54. Energy cannot be _______.

destroyed

14. The work that is done when twice the load is lifted twice the distance is _______.

four times as much

66. The pitch of sound is most closely related to _________.

frequency

22. Compared with the speed of a boat moving across the surface of water, the speed of the bow wave produced is _________.

less

71. Are most elements metallic or nonmetallic?

metallic

59. Dark matter is considered to be __________.

plentiful in the universe

58. Interference is a property of _________.

sound, light, and water waves

16. Emily drops a banana of mass m over the edge of a bridge of height h and it falls to the river below. From the initial PE of the banana converting to KE, find the speed of the banana just before hitting the water.

square root (2gh)

73. Fossil fuels, hydroelectric power, and wind power ultimately get their energy from _______.

the Sun

15. When one does twice the work in twice the time, the power expended is _______.

the same

43. A railroad diesel engine weighs three times as much as a freight car. If the diesel engine coasts at 4 km/h into a freight car that is initially at rest, find the speed of the coupled engine and car.

v = 3.0 km/h

29. For years, marine scientists were mystified by sound waves detected by underwater microphones in the Pacific Ocean. These so-called T-waves were among the purest sounds in nature. Eventually they traced the source to underwater volcanoes, whose rising columns of bubbles resonated like organ pipes. What is the wavelength of a typical T-wave whose frequency is 4.00 Hz? (The speed of sound in seawater is 1530 m/s.)

λ =383 m