Download 1st Sem. Practice and Review

1st Semester Exam Practice and Review - 2011
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. A 15-N force and a 45-N force act on an object in opposite directions. What is the net force on the object?
a. 15 N
b. 30 N
c. 45 N
d. 60 N
e. none of the above
____
2. A clothesline is stretched between two trees. A tire hangs in the middle of the line and the lne is nearly, but
not quite horizontal. The tension in the line on either side of the tire is
a. half the tire’s weight.
b. is less than half the tire’s weight.
c. is more than half the tire’s weight.
____
3. A scalar quantity has
a. only direction.
b. only magnitude.
c. both magnitude and direction.
d. neither magnitude nor direction.
____
4. Equilibrium occurs when
a. all the forces acting on an object are balanced.
b. the sum of the +x forces on an object equals the sum of the –x forces.
c. the net force on the object is zero.
d. the sum of the upward forces equals the sum of the downward forces.
e. all of the above
____
5. Friction is a force that always acts
a. perpendicular to an object's motion.
b. opposite to an object's motion.
c. in the same direction as an object's motion.
____
6. The law of inertia applies to
a. objects at rest.
b. moving objects.
c. both moving and nonmoving objects.
____
7. An object following a straight-line path at constant speed
a. has no forces acting on it.
b. has a net force acting on it in the direction of motion.
c. has zero acceleration.
d. must be moving in a vacuum.
e. none of the above
____
8. How much does a 3.0-kg bag of bolts weigh on Earth?
a. 3.0 kg
b. 3.0 N
c. 10 N
d. 30 N
e. not enough information
____
9. An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the greater mass?
a. The one on Earth
b. The one on the moon
c. They have the same mass.
d. Not enough information to say
____ 10. As an object falls freely in a vacuum, its
a. velocity increases.
b. acceleration increases.
c. both A and B.
d. none of the above.
____ 11. A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During
this time the acceleration of the ball is always
a. in the direction of motion.
b. opposite its velocity.
c. directed downward.
d. directed upward.
____ 12. If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each
second by
a. about 5 m/s.
b. about 10 m/s.
c. about 15 m/s.
d. a variable amount.
e. a rate that depends on its initial speed.
____ 13. In the absence of air resistance, objects fall at constant
a. speed.
b. velocity.
c. acceleration.
d. distances each successive second.
e. all of the above
____ 14. When a basketball player jumps to make a shot, once the feet are off the floor, the jumper's acceleration
a. varies with body orientation.
b. depends on launch speed.
c. is usually greater for taller players (but not always).
d. depends on all the above.
e. is g; no more, no less.
____ 15. A ball is thrown straight up at a velocity of 20 m/s. At the top of its path its instantaneous speed is
a. 0 m/s.
b. about 5 m/s.
c. about 10 m/s.
d. about 20 m/s.
e. about 40 m/s.
____ 16. When representing velocity as a vector,
a. the direction of the arrow shows the direction of motion.
b. the length of the arrow represents the speed.
c. the length of the arrow is drawn to a suitable scale.
d. all of the above
e. none of the above
____ 17. At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same
height. In the absence of air resistance which ball hits the ground first?
a. Neither. They both hit the ground at the same time.
b. The dropped ball
c. The horizontally thrown ball
____ 18. A ball is thrown into the air at some angle. At the very top of the ball's path, its velocity is
a. entirely vertical.
b. There's not enough information given to determine.
c. both vertical and horizontal.
d. entirely horizontal.
____ 19. At what part of a path does a projectile have minimum speed?
a. When it returns to the ground
b. Halfway to the top
c. At the top of its path
d. When it is thrown
e. There's not enough information to say.
____ 20. An object is dropped and falls freely to the ground with an acceleration of g. If it is thrown upward at an angle
instead, its acceleration while in flight would be
a. 0.
b. larger than g.
c. g upward.
d. g downward.
e. none of the above
____ 21. A cannonball is fired at some angle into the air. In the first second it moves 5 meters horizontally. Assuming
it doesn't hit the ground and air resistance is negligible, how far does it move horizontally in the next second?
a. More than 5 m
b. Less than 5 m
c. 5 m
d. Not enough information.
____ 22. In the absence of air resistance, at what other angle will a thrown ball go the same distance as one thrown at
an angle of 75 degrees?
a. 15 degrees.
b. 65 degrees.
c. 70 degrees.
d. 80 degrees.
e. 90 degrees.
____ 23. A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is
a. 10 times as much as the force on the 1-kg book.
b. zero.
c. the same as the force on the 1-kg book.
d. one tenth as much as the force on the 1-kg book
____ 24. Pressure is defined as
a. time per area.
b. velocity per time.
c. force per time.
d. force per area.
e. distance per time.
____ 25. The reason a tennis ball and a solid steel ball of the same volume will accelerate at the same rate, in the
absence of air resistance, is that
a. they have the same mass.
b. the ball with the larger force has the smaller mass.
c. the ball with the larger force also has the larger mass.
d. the force acting on them is the same.
____ 26. If you pull horizontally on a desk with a force of 150 N and the desk doesn't move, the friction force must be
150 N. Now if you pull with 250 N so the desk slides at constant velocity, the friction force is
a. more than 150 N but less than 250 N.
b. 250 N.
c. more than 250.
____ 27. Accelerations are produced by
a. forces.
b. velocities.
c. accelerations.
d. masses.
e. none of the above
____ 28. An apple weighs 1 N. The net force on the apple when it is in free fall is
a. 0 N.
b. 0.1 N.
c. 1 N.
d. 9.8 N.
e. none of the above
____ 29. Aunt Minnie throws a rock downward, and air resistance is negligible. Compared to a rock that is dropped,
the acceleration of the rock after it is thrown is
a. less.
b. the same.
c. more.
____ 30. As a care package falls from a high-flying stationary helicopter, its velocity increases and its acceleration
a. remains the same.
b. decreases.
c. increases.
____ 31. A high school student hits a nail with a hammer. During the collision, there is a force
a. on the nail but not on the hammer.
b. on the nail and also on the hammer.
c. on the hammer but not on the nail.
____ 32. As a ball falls, the action force is the pull of Earth's mass on the ball. What is the reaction to this force?
a. The pull of the ball's mass on Earth
b. The acceleration of the ball
c. Nonexistent in this case
d. Air resistance acting against the ball
e. none of the above
____ 33. A large truck and a small car traveling at the same speed have a head-on collision. The vehicle to undergo the
greater change in velocity will be
a. the small car.
b. the large truck.
c. neither—both are the same
____ 34. As a 600-N woman sits on the floor, the floor exerts a force on her of
a. 6 N.
b. 60 N.
c. 1200 N.
d. 600 N.
e. 6000 N.
____ 35. You drive past a farm, and you see a cow pulling a plow to till a field. You have just learned about Newton’s
third law, and you wonder how the cow is able to move forward if the plow is exerting an equal and opposite
force on the cow. Which of the following explains the movement of the cow and plow?
a. The force exerted by the cow on the plow is equal to the force that the cow exerts on the
ground to move forward.
b. The force exerted by the cow on the plow is larger than the force that the cow exerts on the
ground to move forward.
c. The force exerted by the cow on the plow is smaller than the force that the cow exerts on
the ground to move forward.
d. More information is needed to answer this question.
____ 36. A table tennis ball launcher is fired. Compared to the impulse on the ball, the impulse on the launcher is
a. smaller.
b. larger.
c. the same.
____ 37. Superman is at rest in space when he throws an asteroid that has more mass than he does. Which moves
faster, Superman or the asteroid?
a. Superman
b. The asteroid
c. They both move at the same speed.
____ 38. If the momentum of an object changes and its mass remains constant,
a. it is accelerating (or decelerating).
b. there is a force acting on it.
c. its velocity is changing.
d. all of the above
e. none of the above
____ 39. The reason padded dashboards are used in cars is that they
a. look nice and feel good.
b. decrease the impulse in a collision.
c. increase the force of impact in a collision.
d. decrease the momentum of a collision.
e. increase the time of impact in a collision.
____ 40. A moving freight car runs into an identical car at rest on the track. The cars couple together. Compared to the
velocity of the first car before the collision, the velocity of the combined cars after the collision is
a. zero.
b. one half as large.
c. the same.
d. twice as large.
e. More information is needed to say.
____ 41. If you lift two loads up one story, how much work do you do compared to lifting just one load up one story?
a. One quarter as much
b. One half as much
c. The same amount
d. Twice as much
e. Four times as much
____ 42. The amount of potential energy possessed by an elevated object is equal to
a. the power used to lift it.
b. the distance it is lifted.
c. the force needed to lift it.
d. the work done in lifting it.
e. the value of the acceleration due to gravity.
____ 43. An arrow in a bow has 70 J of potential energy. Assuming no loss of energy to heat, how much kinetic energy
will it have after it has been shot?
a. 0 J
b. 35 J
c. 50 J
d. 70 J
e. 140 J
____ 44. A ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential
energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its
kinetic energy is
a. 100 J.
b. more than 100 J.
c. less than 100 J.
d. Not enough information given.
____ 45. An object that has kinetic energy must have
a. acceleration.
b. a force applied to maintain it.
c. momentum.
d. none of the above
____ 46. Which has greater kinetic energy, a car traveling at 30 km/h or a half-as-massive car traveling at 60 km/h?
a. The 60 km/h car
b. Both have the same kinetic energy.
c. The 30 km/h car
____ 47. A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown
downward hits the ground with 140 J of kinetic energy. Ignoring air friction, with how much kinetic energy
does the second ball hit the ground?
a. less than 140 J
b. 140 J
c. 280 J
d. more than 280 J
e. none of the above
____ 48. Consider molecules of hydrogen gas and molecules of heavier oxygen gas that have the same kinetic energy.
The molecules with the greater speed are
a. hydrogen.
b. Both have the same speed.
c. oxygen.
____ 49. A pulley system can
a. change the direction of a force.
b. multiply the force.
c. increase the amount of work done.
d. Both A and B
e. Both B and C
____ 50. The ratio of useful work output to total work input is called the
a. mechanical advantage.
b. lever arm.
c. pivot point.
d. fulcrum.
e. efficiency.
____ 51. What is the direction of the force that acts on clothes in the spin cycle of a washing machine?
a. Inward
b. Down
c. Outward
d. Up
____ 52. If you whirl a tin can on the end of a string and the string suddenly breaks, the can will
a. fly directly away from you.
b. fly off, tangent to its circular path.
c. fly directly toward you.
d. spiral in toward your hand.
e. spiral away from your hand.
____ 53. A ladybug rests on the bottom of a tin can that is being whirled horizontally on the end of a string. Since the
ladybug, like the can, moves in a circle, there must be a force on it. What exerts this force?
a. Gravity
b. The string
c. There is no force acting on it.
d. The can
e. Your hand
____ 54. A car travels in a circle with constant speed. The net force on the car
a. is zero because the car is not accelerating.
b. is directed forward, in the direction of travel.
c. is directed toward the center of the curve.
d. none of the above
____ 55. Nellie Newton swings a rock into a circular path while holding an attached string overhead. The string makes
a 45-degree angle to the vertical (comprising a "conical pendulum"). The centripetal force that holds the rock
in its circular path is the
a. vertical component of the string tension.
b. horizontal component of the string tension.
c. tension in the string.
d. none of the above
____ 56. Which has greater angular speed, a horse near the outside rail of a merry-go-round or a horse near the inside
rail?
a. Neither—they both have the same angular speed.
b. The inside horse
c. The outside horse
Problem
57. What is the magnitude of the resultant of a 6.0-N force acting vertically upward and a 4.0-N force acting
horizontally?
58. Two people push a refrigerator across a floor. If person A pushes with 80 N of force and person B pushes
with 110 N of force in the same direction, how much frictional force must be acting on the refrigerator to
maintain equilibrium?
59. How much does a 10.0-kg bag of grass seed weigh?
60. What is the average speed of a cheetah that runs 88 m in 5 seconds?
61. A crate falls from a helicopter hovering at an altitude of 1250 m. Neglecting air drag, how long will the crate
take to strike the ground?
62. A package falls out of a helicopter that is traveling horizontally at 70 m/s. It falls into the water below 8.0 seconds later.
Assuming no air resistance, what is the horizontal distance it travels while falling?
63. Kyle throws a ball horizontally from the top of a building that is 5.0 m high. He hopes the ball will reach a swimming
pool that is at the bottom of the building, 12.0 m horizontally from the edge the building. If the ball is to reach the pool,
with what initial speed must Kyle throw it with?
64. Suppose that you exert 300 N horizontally on a 50-kg crate on a factory floor, where friction between the
crate and the floor is 100 N. What is the acceleration of the crate?
65. A 7.0-kg blob of clay moving horizontally at 4.0 m/s hits a 5.0-kg blob of clay at rest. What is the speed of
the two blobs stuck together immediately after the collision?
66. A 40.0-kg football player leaps through the air to collide with and tackle a 50.0-kg player heading toward
him, also in the air. If the 40.0-kg player is heading to the right at 9.0 m/s and the 50.0-kg player is heading
toward the left at 2.0 m/s, what is the speed and direction of the tangled players?
67. A 3.00 kg toy falls from a height of 1.00 m. What will the kinetic energy of the toy be just before the toy hits
the ground?
68. Old Faithful geyser in Yellowstone National Park shoots water every hour to a height of 40.0 m. With what
velocity does the water leave the ground? Use energy relationships to solve, not kinematic equations.
69. A 0.500 kg mass is swung on a conical pendulum in a circle with a radius of 0.500 m. Find the tangential
speed of the mass if the centripetal force acting on the mass is 2.13 N.
70. Find the tangential speed of a of a toy train that circles a 1.5 m radius track every 10.0s.
71. You push with 10.0 N on a 5.0-kg block and there are no opposing forces. At what rate will the block
accelerate?
72. What is the average power supplied by a 60.0 kg person running up a flight of stairs a vertical distance of 4.0
m in 4.2 s?
Final Exam Practice and Review
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
B
C
B
E
B
C
C
D
B
A
C
B
C
E
A
D
A
D
C
D
C
A
A
D
C
B
A
C
B
A
B
A
A
D
C
C
A
D
E
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
B
D
D
D
C
C
A
B
A
D
E
A
B
D
C
B
A
PROBLEM
57. ANS:
7.2 N
58. ANS:
190 N
59. ANS:
100 N
60. ANS:
17.6 m/s
61. ANS:
15.8 s
62. ANS:
560 m
63. ANS:
12.0 m/s
64. ANS:
4 m/s2
65. ANS:
2.3 m/s
66. ANS:
2.9 m/s toward the right
67. ANS:
30.0 J
68. ANS:
28.3 m/s
69. ANS:
1.46 m/s
70. ANS:
0.942 m/s
71. ANS:
2.0 m/s2
72. ANS:
570 W