1. Physics 100 Review for Final Exam

2. Which of these is not a scientific hypothesis?
Protons carry an electric charge.
Undetectable particles are some of nature’s secrets.
Charged particles bend when in a magnetic field.
All of the above are scientific hypotheses.
Answer: B

3. Which of these is not a scientific hypothesis?
Protons carry an electric charge.
Undetectable particles are some of nature’s secrets.
Charged particles bend when in a magnetic field.
All of the above are scientific hypotheses.
If protons didn’t carry electric charge, they wouldn’t be deflected when crossing a magnetic field. This would be a test for showing the hypothesis wrong. So both A and C are capable of being proved wrong, which makes them scientific. Statement B, however, has no test for wrongness. It is reasonable speculation—but not a scientific hypothesis.
Explanation: Choices A and C can be disproved by experiments.
Choice B has no test for wrongness, so it is not a scientific hypothesis.

4. Which of these is a scientific hypothesis?
The Moon is made of green cheese.
Atomic nuclei are the smallest particles in nature.
A magnet will pick up a copper penny.
Cosmic rays cannot penetrate the thickness of your Conceptual Physics textbook.
A., B., C., D.

5. The Moon is made of green cheese.
Which of these is a scientific hypothesis?
The Moon is made of green cheese.
Atomic nuclei are the smallest particles in nature.
A magnet will pick up a copper penny.
Cosmic rays cannot penetrate the thickness of your Conceptual Physics textbook.
All are scientific hypotheses! All choices not only have tests for proving wrongness, but have been proved wrong. Nevertheless, they still pass the test of being a scientific hypothesis
Explanation: All are scientific hypotheses! All have tests for proving wrongness, so they pass the test of being a scientific hypothesis.

6. Which of these often changes over time with further study?
Facts.
Theories.
Both of the above.
Neither of the above.
Answer: C

7. Which of these often changes over time with further study?
Facts.
Theories.
Both of the above.
Neither of the above.
Both can change. Is this a weakness or strength of science? For example, if everything a child holds true is unchanged when that child grows up, with years of study, even receiving advanced degrees, then either nothing was learned or the child was unusually gifted from the start—or was part of a closed system. As we learn new information, we refine our ideas. Likewise with the fields of science.
Explanation: Both can change. As we learn new information, we refine our ideas; likewise in science.

8. vast synthesis of well-tested hypotheses and facts.
A person who says, “that’s only a theory” likely doesn’t know that a scientific theory is a
guess.
number of facts.
hypothesis of sorts.
vast synthesis of well-tested hypotheses and facts.
Answer: D

9. vast synthesis of well-tested hypotheses and facts.
A person who says, “that’s only a theory” likely doesn’t know that a scientific theory is a
guess.
number of facts.
hypothesis of sorts.
vast synthesis of well-tested hypotheses and facts.
Theory in everyday speech is vastly different than its use in science. A vast and verifiable body of knowledge isn’t only a theory; if it passes all its tests, it is elevated to that status! Newton’s theory of gravity and Einstein’s theory of relativity, for example, are not idle hypotheses—both are supported by innumerable experiments. They are more than only theories.
Explanation: The word “theory” in everyday speech is different than its use in science.
In science, only a vast, experimentally verifiable body of knowledge is a theory.

10. ? What is the net force acting on the box? 15 N to the left
15 N to the right
5 N to the left
5 N to the right ?
Answer: D 10

11. What is the net force acting on the box? 15 N to the left
15 N to the right
5 N to the left
5 N to the right
When you take a 10N force to the right added to a 5 N force to the left, because the two forces are in opposite directions, they in fact subtract, rather than add.
So, the larger 10N force to the right is cut back by the 5N force to the left, so that the remaining force i.e. the Net force is only 5N to the right. 11

12. When you stand on two bathroom scales with one foot on each scale and with your weight evenly distributed, each scale will read
your weight.
half your weight.
zero.
more than your weight.
Answer: B 12

13. When you stand on two bathroom scales with one foot on each scale and with your weight evenly distributed, each scale will read
your weight.
half your weight.
zero.
more than your weight.
You are at rest on the scales, so F = 0. The sum of the two upward support forces is equal to your weight.
Your weight is distributed over the two scales. So, each scale reads half your weight.
Explanation:
You are at rest, so F=0.
Forces from both scales add to cancel your weight.
Force from each scale is one-half your weight 13

14. not enough information
You are pushing a crate at a constant speed in a straight line. If the friction force is 75 N, how much force must you apply?
more than 75 N
less than 75 N
equal to 75 N
not enough information
Answer: C 14

15. You are pushing a crate at a constant speed in a straight line
You are pushing a crate at a constant speed in a straight line. If the friction force is 75 N, how much force must you apply?
A. more than 75 N
B. less than 75 N
C. equal to 75 N
D. not enough information
Crate is in dynamic equilibrium, So there is no NET force acting on it
So you must apply a force that balances out the force of friction. Which means it must be equal and opposite to the force of friction. So if Friction is 75N to the left, the Applied Force from you is 75N to the right.
Explanation:
The crate is in dynamic equilibrium, so, F = 0.
Your applied force balances the force of friction. 15

16. The average speed of driving 30 km in 1 hour is the same as the average speed of driving
30 km in 2 hours.
60 km in 1/2 hour.
60 km in 2 hours. 16

17. The average speed of driving 30 km in 1 hour is the same as the average speed of driving
30 km in 2 hours.
60 km in 1/2 hour.
60 km in 2 hours.
Explanation:
Average speed = total distance / time
So, average speed = 30 km / 1 h = 30 km/h.
Now, if we drive 60 km in 2 hours:
Average speed = 60 km / 2 h = 30 km/h
Same 17

18. An automobile is accelerating when it is slowing down to a stop.
rounding a curve at a steady speed.
Both of the above.
Neither of the above. 18

19. rounding a curve at a steady speed. Both of the above.
An automobile is accelerating when it is
slowing down to a stop.
rounding a curve at a steady speed.
Both of the above.
Neither of the above.
Explanation:
Change in speed (increase or decrease) is acceleration, so slowing is acceleration.
Change in direction is acceleration (even if speed stays the same), so rounding a curve is acceleration.
Acceleration occurs due to a change in either speed or direction (or both).
When a car slows down it changes its speed, so it is accelerating.
When a car rounds a curve, although its speed is steady it is accelerating because it is changing direction. 19

20. Acceleration and velocity are actually the same.
rates but for different quantities.
the same when direction is not a factor.
the same when an object is freely falling. 20

21. Acceleration and velocity are actually
the same.
rates but for different quantities.
the same when direction is not a factor.
the same when an object is freely falling.
Explanation:
Velocity is the rate at which distance changes over time,
Acceleration is the rate at which velocity changes over time. 21

22. the same. 35 m/s. more than 35 m/s. 60 m/s.
A free-falling object has a speed of 30 m/s at one instant. Exactly 1 s later its speed will be
the same.
35 m/s.
more than 35 m/s.
60 m/s. 22

23. the same. 35 m/s. more than 35 m/s. 60 m/s.
A free-falling object has a speed of 30 m/s at one instant. Exactly 1 s later its speed will be
the same.
35 m/s.
more than 35 m/s.
60 m/s.
The object gains 10m/s after every second.
So, at a given instance, if its speed is 30m/s, then a second later it will be 10m/s greater than that i.e. 30m/s + 10m/s = 40m/s
So, Its speed a second later is 40m/s which is more than 35m/s.
Explanation:
One second later its speed will be 40 m/s, which is more than 35 m/s. 23

24. A. less than Sanjay’s push. equal to Sanjay’s push.
When Sanjay pushes a refrigerator across a kitchen floor at a constant speed, the force of friction between the refrigerator and the floor is
A. less than Sanjay’s push.
equal to Sanjay’s push.
equal and opposite to Sanjay’s push.
more than Sanjay’s push.
C. equal and opposite to Sanjay’s push.

25. A. less than Sanjay’s push. equal to Sanjay’s push.
When Sanjay pushes a refrigerator across a kitchen floor at a constant speed, the force of friction between the refrigerator and the floor is
A. less than Sanjay’s push.
equal to Sanjay’s push.
equal and opposite to Sanjay’s push.
more than Sanjay’s push.
C. equal and opposite to Sanjay’s push.

26. A. less than Sanjay’s push. equal to Sanjay’s push.
When Sanjay pushes a refrigerator across a kitchen floor at an increasing speed, the amount of friction between the refrigerator and the floor is
A. less than Sanjay’s push.
equal to Sanjay’s push.
equal and opposite to Sanjay’s push.
more than Sanjay’s push.
A. less than Sanjay’s push.

27. When Sanjay pushes a refrigerator across a kitchen floor at an increasing speed, the amount of friction between the refrigerator and the floor is
A. less than Sanjay’s push.
equal to Sanjay’s push.
equal and opposite to Sanjay’s push.
more than Sanjay’s push.
Explanation:
The increasing speed indicates a net force greater than zero. The refrigerator is not in equilibrium.
A. less than Sanjay’s push.

28. Consider a cart pushed along a track with a certain force
Consider a cart pushed along a track with a certain force. If the force remains the same while the mass of the cart decreases to half, the acceleration of the cart
remains relatively the same.
halves.
doubles.
changes unpredictably. 28

29. Acceleration = net force / mass
Consider a cart pushed along a track with a certain force. If the force remains the same while the mass of the cart decreases to half, the acceleration of the cart
remains relatively the same.
halves.
doubles.
changes unpredictably.
Explanation:
Acceleration = net force / mass
Because, mass is in the denominator, acceleration increases as mass decreases.
So, if mass is halved, acceleration doubles.
Explanation:
Acceleration = Net Force / Mass.
So, if…
Mass is halved i.e. Mass is now ½ Mass
Net Force is kept the same i.e. Net Force
New Acceleration = New Net Force / New Mass 29

30. At one instant, an object in free fall has a speed of 40 m/s
At one instant, an object in free fall has a speed of 40 m/s. Its speed 1 second later is
A. also 40 m/s.
45 m/s.
50 m/s.
None of the above.
C m/s.

31. At one instant, an object in free-fall has a speed of 40 m/s
At one instant, an object in free-fall has a speed of 40 m/s. Its speed 1 second later is
A. also 40 m/s.
45 m/s.
50 m/s.
None of the above.
Explanation:
Anything in free fall increases the falling speed by about 10 meters/second every second.
C m/s.

32. A 5-kg iron ball and a 10-kg iron ball are dropped from rest
A 5-kg iron ball and a 10-kg iron ball are dropped from rest. For negligible air resistance, the acceleration of the heavier ball will be
A. less.
the same.
more.
undetermined.
B. the same.

33. A 5-kg iron ball and a 10-kg iron ball are dropped from rest
A 5-kg iron ball and a 10-kg iron ball are dropped from rest. For negligible air resistance, the acceleration of the heavier ball will be
A. less.
the same.
more.
undetermined.
B. the same.

34. If a 50-N person is to fall at terminal velocity, the air resistance needed is
A. less than 50 N.
50 N.
more than 50 N.
None of the above.
B N.

35. Then, F = 0 and acceleration = 0.
If a 50-N person is to fall at terminal velocity, the air resistance needed is
A. less than 50 N.
50 N.
more than 50 N.
None of the above.
Explanation:
Then, F = 0 and acceleration = 0.
B N.

36. As a skydiver falls faster and faster through the air, air resistance
A. increases.
decreases.
remains the same.
Not enough information.
A. increases.

37. As a skydiver falls faster and faster through the air, air resistance
A. increases.
decreases.
remains the same.
Not enough information.
A. increases.

38. As a skydiver fall faster and faster through the air, net force
A. increases.
decreases.
remains the same.
Not enough information.
B. decreases.

39. As a skydiver fall faster and faster through the air, net force
A. increases.
decreases.
remains the same.
Not enough information.
Explanation: The net force is the combined force on the skydiver. As the air resistance builds up, it cancels out more and more of the gravitational force, which results in a smaller net force.
B. decreases.

40. As a skydiver fall faster and faster through the air, her acceleration
A. increases.
decreases.
remains the same.
Not enough information.
B. decreases.

41. As the skydiver faster and faster through the air, her acceleration
A. increases.
decreases.
remains the same.
Not enough information.
Explanation
If the net force decreases, so much the acceleration according to F=ma. (Newton’s 2nd Law)
B. decreases.

42. When the air in a tube containing a coin and a feather is removed,
A. the feather hits the bottom first, before the coin hits.
the coin hits the bottom first, before the feather hits.
both the coin and feather drop together side-by-side.
Not enough information.
C. both the coin and feather drop together side-by-side.

43. When the air in a tube containing a coin and a feather is removed,
A. the feather hits the bottom first, before the coin hits.
the coin hits the bottom first, before the feather hits.
both the coin and feather drop together side- by-side.
Not enough information.
Explanation: With no air resistance, they are in free fall and accelerate at the same rate: g or 9.8 m/s2
C. both the coin and feather drop together side-by-side.

44. Depends on the speed of the lift
Work is done in lifting a barbell. How much work is done in lifting a barbell that is twice as heavy the same distance?
A. Twice as much
Half as much
The same
Depends on the speed of the lift
A. Twice as much.

45. Depends on the speed of the lift
Work is done in lifting a barbell. How much work is done in lifting a barbell that is twice as heavy the same distance?
A. Twice as much
Half as much
The same
Depends on the speed of the lift
Explanation:
This is in accord with work  force  distance. Twice the force for the same distance means twice the work done on the barbell.
A. Twice as much.

46. A. less than twice as much. twice as much. more than twice as much.
You do work when pushing a cart with a constant force. If you push the cart twice as far, then the work you do is
A. less than twice as much.
twice as much.
more than twice as much.
zero.
B. twice as much.

47. A. less than twice as much. twice as much. more than twice as much.
You do work when pushing a cart with a constant force. If you push the cart twice as far, then the work you do is
A. less than twice as much.
twice as much.
more than twice as much.
zero.
B. twice as much.

48. A job can be done slowly or quickly
A job can be done slowly or quickly. Both may require the same amount of work, but different amounts of
A. energy.
momentum.
power.
impulse.
C. power.

49. Power is the rate at which work is done.
A job can be done slowly or quickly. Both may require the same amount of work, but different amounts of
A. energy.
momentum.
power.
impulse.
Comment:
Power is the rate at which work is done.
C. power.

50. The work done in bringing a moving car to a stop is the force of tire friction  stopping distance. If the initial speed of the car is doubled, the stopping distance is
A. actually less.
about the same.
twice.
None of the above.
D. none of the above.

51. The work done in bringing a moving car to a stop is the force of tire friction  stopping distance. If the initial speed of the car is doubled, the stopping distance is
A. actually less.
about the same.
twice.
None of the above.
Explanation:
Twice the speed means four times the kinetic energy and four times the stopping distance.
D. none of the above.

52. A certain machine is 30% efficient. This means the machine will convert
A. 30% of the energy input to useful work—70% of the energy input will be wasted.
70% of the energy input to useful work—30% of the energy input will be wasted.
Both of the above.
None of the above.
A. 30% of the energy input to useful work—70% of the energy input will be wasted.

53. A certain machine is 30% efficient. This means the machine will convert
A. 30% of the energy input to useful work— 70% of the energy input will be wasted.
70% of the energy input to useful work—30% of the energy input will be wasted.
Both of the above.
None of the above.
A. 30% of the energy input to useful work—70% of the energy input will be wasted.

54. There is not enough information.
A 1-meter-long pendulum has a bob with a mass of 1 kg. Suppose that the bob is now replaced with a different bob of mass 2 kg, how will the period of the pendulum change?
A. It will double.
It will halve.
It will remain the same.
There is not enough information.
C. It will remain the same.

55. There is not enough information.
A 1-meter-long pendulum has a bob with a mass of 1 kg. Suppose that the bob is now replaced with a different bob of mass 2 kg, how will the period of the pendulum change?
A. It will double.
It will halve.
It will remain the same.
There is not enough information.
C. It will remain the same.
Explanation: The period of a pendulum depends only on the length of the pendulum, not on the mass. So changing the mass will not change the period of the pendulum.

56. If the frequency of a particular wave is 20 Hz, its period is
A. 1/20 second.
20 seconds.
more than 20 seconds.
None of the above.
A. 1/20 second.

57. If the frequency of a particular wave is 20 Hz, its period is
A. 1/20 second.
20 seconds.
more than 20 seconds.
None of the above.
Explanation:
Note when  = 20 Hz, T = 1/ = 1/(20 Hz) = 1/20 second.
A. 1/20 second.

58. The vibrations along a transverse wave move in a direction
A. along the wave.
perpendicular to the wave.
Both A and B.
Neither A nor B.
B. perpendicular to the wave.

59. The vibrations along a transverse wave move in a direction
A. along the wave.
perpendicular to the wave.
Both A and B.
Neither A nor B.
Comment:
The vibrations in a longitudinal wave, in contrast, are along (or parallel to) the direction of wave travel.
B. perpendicular to the wave.

60. The Doppler effect occurs for
A. sound.
light.
Both A and B.
Neither A nor B.
C. both A and B.

61. The Doppler effect occurs for
A. sound.
light.
Both A and B.
Neither A nor B.
Explanation:
The Doppler effect occurs for both sound and light. Astronomers measure the spin rates of stars by the Doppler effect.
C. both of the above.

62. Interference is a property of
A. sound.
light.
Both A and B.
Neither A nor B.
C. Both A and B.

63. Interference is a property of
A. sound.
light.
Both A and B.
Neither A nor B. .
C. Both A and B.