16) A 777 aircraft has a mass of 300,000 kg. At a certain instant during its landing, its speed is 27.0 m/s. If the
braking force is 480,000 N, how much further does it travel along the runway before it comes to a stop?
A) 40.5 m
B) 142 m
C) 181 m
D) 228 m
17) What average net force is required to accelerate a car with a mass of 1200 kg from 0 to 27.0 m/s in 10.0 s?
A) 444 N
B) 3240 N
C) 4360 N
D) 11800 N
18) A net force of 450 N applied to a car results in the car accelerating at 0.360 m/s2. What is the mass of the car?
A) 162 kg
B) 12300 kg
C) 1250 kg
D) 1590 kg
19) A catcher stops a ball traveling at 40 m/s in a distance of 20 cm and feels a force of 600 N against his glove.
What is the mass of the ball?
A) 0.15 kg
B) 0.20 kg
C) 0.25 kg
D) 0.30 kg
20) To determine the mass of a car, a student (with a friend at the wheel) pushes the car holding a bathroom scale
between himself and the car and carefully maintains a constant reading of 400 N on the scale while the car
accelerates on level ground. At the conclusion of the experiment his friend reports that the car accelerated from rest
to 14.0 km/hr in 12.0 s. What was the mass of the car?
A) 343 kg
B) 1230 kg
C) 3360 kg
D) 3430 kg
21) A truck is towing a car whose mass is one quarter that of the truck. The force exerted by the truck on the car is
6000 N. The force exerted by the car on the truck is
A) 1500 N.
B) 24000 N.
C) 3000 N.
D) 6000 N.
24) Two boxes, one more massive than the other, rest in contact with one another on a smooth, level floor. A
horizontal force F pushes on one or the other of the boxes. The contact force between the boxes
A) is larger when F is applied to the more massive box.
B) is larger when F is applied to the less massive box.
C) is equal in both cases.
D) can be larger or smaller depending on the actual masses.
29) The mass of the Moon is about 1/80th of the mass of Earth. The force exerted by Earth on the Moon is about 80
times that exerted by the Moon on Earth.
Answer: FALSE
30) The force you exert on Earth is insignificant compared to the force Earth exerts on you.
Answer: FALSE
31) A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the
3.0-kg box pushing it against the 5.0-kg box, and, as a result, both boxes slide along the floor. How large is the
contact force between the two boxes?
A) 12 N
B) 20 N
C) 32 N
D) 0 N
32) A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the
5.0-kg box pushing it against the 3.0-kg box, and, as a result, both boxes slide along the floor. How large is the
contact force between the two boxes?
A) 12 N
B) 20 N
C) 32 N
D) 0 N
33) Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with
the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two
masses. What is the contact force between the 5.0-kg mass and the 3.0-kg mass?
A) 0 N
B) 10 N
C) 25 N
D) 40 N
34) Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with
the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two
masses. What is the contact force between the 3.0-kg mass and the 2.0-kg mass?
A) 0 N
B) 10 N
C) 25 N
D) 40 N
36) Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with
the 3.0-kg mass in the center. A force of 50 N pushes on the 2.0-kg mass, which pushes against the other two
masses. What is the contact force between the 3.0-kg mass and the 2.0-kg mass?
A) 0 N
B) 10 N
C) 25 N
D) 40 N
37) A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the
locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. Neglect friction. What is
the force between the 80,000-kg and 50,000-kg wagons?
A) 35,000 N
B) 40,000 N
C) 60,000 N
D) 65,000 N
38) A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the
locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. Neglect friction. What is
the force between the 50,000-kg and 70,000-kg wagons?
A) 35,000 N
B) 40,000 N
C) 60,000 N
D) 65,000 N
39) A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the
locomotive has a mass of 70,000 kg, the next one, 50,000 kg, and the last one, 80,000 kg. Neglect friction. What is
the force between the 80,000-kg and 50,000-kg wagons?
A) 35,000 N
B) 40,000 N
C) 60,000 N
D) 65,000 N
40) A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the
locomotive has a mass of 70,000 kg, the next one, 50,000 kg, and the last one, 80,000 kg. Neglect friction. What is
the force between the 70,000-kg and 50,000-kg wagons?
A) 35,000 N
B) 40,000 N
C) 60,000 N
D) 65,000 N
41) A 1200-kg car is pulling a 500-kg trailer along level ground. Friction is negligible. The car accelerates with an
acceleration of 1.3 m/s2. What is the force exerted by the car on the trailer?
A) 600 N
B) 650 N
C) 700 N
D) 750 N
42) A flatbed truck is carrying a load of timber which is not tied down. The mass of the timber is 800 kg. The
maximum frictional force between the truck bed and the load is 2400 N. What is the highest acceleration that the
truck can have without losing its load?
43) A locomotive is pulling a number of identical wagons along a level track and accelerating. Friction is
negligible. Starting from the last wagon, the ratio of the forces between adjacent wagons is
A) 1:2:3:4 . . .
B) 1:2:4:8 . . .
1 1 1
1: : :
C) 2 4 8 . . .
D) 1:1:1:1 . . .
44) A load is being lifted by means of two cables attached to it. The first cable exerts a force of 600 N at an angle of
35° to the left of the vertical. The second cable exerts a force of 1300 N. If the load is accelerating vertically, at what
angle to the right of the vertical is the second cable pulling?
A) 15.4°
B) 16.2°
C) 67.8°
D) 75.8°
45) A 50.0-kg crate is being pulled along a horizontal, smooth surface. The pulling force is 10.0 N and is directed
20.0° above the horizontal. What is the acceleration of the crate?
A) 0.0684 m/s2
B) 0.188 m/s2
C) 0.200 m/s2
D) 0.0728 m/s2
46) A 40.0-kg box is being pushed along a horizontal, smooth surface. The pushing force is 15.0 N directed at an
angle of 15.0° below the horizontal. What is the acceleration of the crate?
A) 0.158 m/s2
B) 0.362 m/s2
C) 0.466 m/s2
D) 0.375 m/s2
47) A 1000-kg barge is being towed by means of two horizontal cables. One cable is pulling with a force of 80.0 N
in a direction 30.0° west of north. In what direction should the second cable pull so that the barge will accelerate
northward, if the force exerted by the cable is 120 N?
A) 19.5° east of north
B) 21.1° east of north
C) 47.5° east of north
D) 54.7° east of north
48) A 1000-kg barge is being towed by means of two horizontal cables. One cable is pulling with a force of 80.0 N
in a direction 30.0° west of north. The second cable pulls in a direction 20.0° east of north. What should the
magnitude of its pulling force be so that the barge will accelerate northward?
A) 127 N
B) 120 N
C) 117 N
D) 73.7 N
49) An object is being acted upon by three forces and moves with a constant velocity. One force is 60.0 N along the
x-axis, the second is 75.0 N along the y-axis. What is the magnitude of the third force?
A) 135 N
B) 15.0 N
C) 48.0 N
D) 96.0 N
50) An object is being acted upon by three forces and moves with a constant velocity. One force is 60 N along the
x-axis, the second is 75 N along the y-axis. What is the direction of the third force, measured counterclockwise from
the x-axis?
A) 128°
B) 182°
C) 213°
D) 231°
51) An object is being acted upon by three forces and moves with a constant velocity. One force is 60 N along the
x-axis, the second is 75 N along a direction making a counterclockwise angle of 150° with the x-axis. What is the
direction of the third force, measured counterclockwise from the x axis?
A) 128°
B) 182°
C) 226°
D) 262°
52) An object is being acted upon by three forces and moves with a constant velocity. One force is 60.0 N along the
x-axis, the second is 75.0 N along a direction making a counterclockwise angle of 150.0° with the x-axis. What is the
magnitude of the third force?
A) 37.8 N
B) 62.4 N
C) 130 N
D) 135 N
53) An object is being acted upon by three forces and moves with a constant velocity. One force is 60 N along the
x-axis, the second is 75 N along a direction making a clockwise angle of 150° with the x-axis. What is the direction
of the third force, measured clockwise from the x-axis?
A) 164°
B) 146°
C) 236°
D) 262°
54) The mass of an object is fixed, but its weight varies from location to location.
Answer: TRUE
55) A ball is thrown up into the air. At the highest point in its trajectory, the net force acting on it is
A) equal to its weight.
B) greater than its weight.
C) less than its weight, but not zero N.
D) zero N.
56) A ball is thrown up into the air. Ignore air resistance. When it is rising and reaches half of its maximum height,
the net force acting on it is
A) equal to its weight.
B) greater than its weight.
C) less than its weight, but not zero N.
D) zero N.
57) A fireman is sliding down a fire pole. As he speeds up, he tightens his grip on the pole, thus increasing the
vertical frictional force that the pole exerts on the fireman. When this force equals the weight of the fireman, what
happens?
A) The fireman comes to a stop.
B) The fireman descends with slower and slower speed.
C) The fireman descends with a smaller acceleration.
D) The fireman continues to descend, but with constant speed.
58) A person has a mass of 45 kg. How much does she weigh?
A) 4.6 N
B) 20 N
C) 99 N
D) 440 N
59) A person has a mass of 45 kg. How much does she weigh on the Moon, where g = 1.62 m/s2?
A) 45 N
B) 73 N
C) 7.4 N
D) 440 N
60) An astronaut weighs 99.0 N on the Moon, where the acceleration of gravity is 1.62 m/s 2. How much does she
weigh on Earth?
A) 61.0 N
B) 99.0 N
C) 600 N
D) 440 N
62) A 40.0-kg crate is being lowered by means of a rope. Its downward acceleration is 2.00 m/s 2. What is the force
exerted by the rope on the crate?
A) 40.0 N
B) 232 N
C) 312 N
D) 472 N
63) A 40.0-kg crate is being raised by means of a rope. Its upward acceleration is 2.00 m/s 2. What is the force
exerted by the rope on the crate?
A) 312 N
B) 392 N
C) 472 N
D) 552 N
64) A person is lowering a bucket into a well with a constant speed. The force exerted by the rope on the bucket is
A) equal to the bucket's weight.
B) greater than the bucket's weight.
C) less than the bucket's weight, but not zero N.
D) zero N.
65) A 45-kg person steps on a scale in an elevator. The scale reads 460 N. What is the elevator doing?
Answer: It is accelerating upward at 0.41 m/s2.
66) A 4.5.0-kg person steps on a scale in an elevator. The scale reads 460 N. What is the magnitude of the
acceleration of the elevator?
A) 9.81 m/s2
B) 46.9 m/s2
C) 0.206 m/s2
D) 0.412 m/s2
Answer: D
67) A 47.0-kg person steps on a scale in an elevator. The scale reads 461 N. What is the elevator doing?
Answer: It is either at rest or traveling with a constant velocity.
68) A student uses a plumb bob to verify that the doorjamb in a car is vertical. As the car pulls away from a stop,
the student observes that the string now makes an angle  with the doorjamb. Why does this happen?
Answer: The car and the plumb bob are both accelerating. The force exerted by the string on the plumb bob
must have a forward component, and the string pulls along its own length, so it cannot be vertical.
69) A student uses a plumb bob to verify that the doorjamb in a car is vertical. As the car pulls away from a stop,
the student observes that the string now makes an angle  with the doorjamb. What is the acceleration of the car?
A) g sin 
B) g cos 
C) g tan 
D) g 
70) The locking mechanism for the seatbelt of a car makes use of the fact that the apparent vertical direction (i.e.
the direction in which a plumb bob hangs) changes with the car's deceleration. In a certain collision, the deceleration
of a car is 5.00 g. What angle doe the apparent vertical make with the true vertical?
Answer: 78.7°
71) A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 35.0° on
either side of the vertical direction. What is the tension in each cable?
A) 231 N
B) 400 N
C) 2390 N
D) 3920 N
72) A 10.0-kg picture is held in place by two wires, one hanging at 35.0° to the left of the vertical and the other at
45.0° to the right of the vertical. What is the tension in the first wire?
A) 70.4 N
B) 50.8 N
C) 98.1 N
D) 69.4 N
73) A 10.0-kg picture is held in place by two wires, one hanging at 45.0° to the left of the vertical and the other at
45.0° to the right of the vertical. What is the tension in the second wire?
A) 71.8 N
B) 69.4 N
C) 98.1 N
D) 50.8 N
74) What does the word "normal" mean in the phrase "normal force"?
A) the force that is usually exerted by a surface
B) the total force exerted by a surface
C) the component of the force exerted by a surface parallel to the surface
D) the component of the force exerted by a surface perpendicular to the surface
75) A 120-kg mass rests on a horizontal surface. What is the magnitude of the normal force exerted by the surface
on the mass?
Answer: 1180 N
76) A 40.0-kg suitcase is being pulled along the ground by means of a strap which exerts a force of 10.0 N at an
angle of 51.0° above the horizontal. What is the normal force exerted by the ground?
A) 17.1 N
B) 15.7 N
C) 384 N
D) 398 N
Answer: C
Diff: 1
Page Ref: Sec. 5-7
77) A 30.0-kg object slides down a slope which is inclined 27.0° to the horizontal. What is the normal force on the
object?
A) 171 N
B) 262 N
C) 387 N
D) 398 N
78) An object rests on an inclined surface. If the inclination of the surface is made steeper, what does the normal
force on the object do?
A) increase
B) decrease
C) stays the same
D) The normal force is zero N.
79) An ant walks down the surface of a ball. If the ant begins to slip when the normal force is less than one-third of
the ant's weight, at what angle, measured from the top of the ball, does the ant begin to slip?
A) 70.5°
B) 19.5°
C) 18.4°
D) 35.2°
80) An ant walks down the surface of a ball. If the ant begins to slip when the normal force is less than one-third of
the tangential component of the ant's weight, at what angle, measured from the top of the ball, does the ant begin to
slip?
A) 70.5°
B) 19.5°
C) 18.4°
D) 35.2°
81) Imagine that the metal head of a hammer is loose. In order to get the hammerhead tight again you should
A) drop the hammer on its side from some given height.
B) drop the hammer with the handle end down.
C) drop the hammer with the head end down.
D) It makes no difference how you drop the hammer.
Figure 5-1
82) In Figure 5-1, masses m1 and m2 are such that m1 > m2 and they lay on a level, frictionless surface. We can apply
a horizontal force F either from the left or from the right. The contact force between masses m 1 and m2 is
A) larger when F is applied from the left.
B) larger when F is applied from the right.
C) the same in either case.
D) impossible to determine based on this data.