University Physics with Modern Physics 14th Edition By Young – Test Bank

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Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) A 615 N student standing on a scale in an elevator notices that the scale reads 645 N.
From this information, the student knows that the elevator must be moving
A) upward.
B) downward.
C) You cannot tell if it is moving upward or downward.
1)
Answer: C
2) Which one of the following free-body diagrams best represents the free-body diagram,
with correct relative force magnitudes, of a person in an elevator that is traveling
upward with an unchanging velocity? F f is the force of the floor on the person and F g
is the force of gravity on the person.
A)
B)
C)
D)
2)
1
E)
Answer: B
3) Which one of the following free-body diagrams best represents the free-body diagram,
with correct relative force magnitudes, of a person in an elevator that is traveling
upward but is gradually slowing down at a rate of 9 m/s2? F f is the force of the floor
on the person and F g is the force of gravity on the person.
A)
B)
C)
D)
E)
3)
Answer: D
2
4) Two weights are connected by a massless wire and pulled upward with a constant
speed of 1.50 m/s by a vertical pull P. The tension in the wire is T (see figure). Which
one of the following relationships between T and P must be true?
A) T = P
B) P = T + 25 N
C) P + T = 125 N
D) P = T + 100 N
E) T > P
4)
Answer: B
3
5) Two objects having masses m1 and m2 are connected to each other as shown in the
figure and are released from rest. There is no friction on the table surface or in the
pulley. The masses of the pulley and the string connecting the objects are completely
negligible. What must be true about the tension T in the string just after the objects are
released?
A) T =
m2g
B) T <
m2g
C) T =
m1g
D) T >
m1g
E) T >
m2g
5)
Answer: B
6) Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The
mass of P is greater than that of Q. A horizontal force F (of magnitude F) is applied to
Q as shown in the figure, accelerating the bodies to the right. The magnitude of the
force exerted by the connecting cord on body P will be
A) greater than F. B) less than F but not zero.
C) equal to F. D) zero.
6)
Answer: B
4
7) Two unequal masses M and m (M > m) are connected by a light cord passing over a
pulley of negligible mass, as shown in the figure. When released, the system
accelerates. Friction is negligible. Which figure below gives the correct free-body force
diagrams for the two masses in the moving system?
A) B) C) D)
7)
Answer: C
8) Two objects have masses m and 5m, respectively. They both are placed side by side on
a frictionless inclined plane and allowed to slide down from rest.
A) It takes the heavier object 5 times longer to reach the bottom of the incline than
the lighter object.
B) It takes the lighter object 10 times longer to reach the bottom of the incline than
the heavier object.
C) It takes the lighter object 5 times longer to reach the bottom of the incline than the
heavier object.
D) The two objects reach the bottom of the incline at the same time.
E) It takes the heavier object 10 times longer to reach the bottom of the incline than
the lighter object.
8)
Answer: D
5
9) A box slides down a frictionless plane inclined at an angle θ above the horizontal. The
gravitational force on the box is directed
A) parallel to the plane in the same direction as the movement of the box.
B) parallel to the plane in the opposite direction as the movement of the box.
C) at an angle θ below the inclined plane.
D) vertically.
E) perpendicular to the plane.
9)
Answer: D
10) A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector
sum of all the forces acting on this crate must point down the ramp.
A) True B) False
10)
Answer: B
11) A brick is resting on a rough incline as shown in the figure. The friction force acting on
the brick, along the incline, is
A) less than the weight of the brick. B) greater than the weight of the brick.
C) equal to the weight of the brick. D) zero.
11)
Answer: A
12) A woman is straining to lift a large crate, without success because it is too heavy. We
denote the forces on the crate as follows: P is the upward force the woman exerts on
the crate, C is the vertical contact force exerted on the crate by the floor, and W is the
weight of the crate. How are the magnitudes of these forces related while the woman is
trying unsuccessfully to lift the crate?
A) P = C B) P + C > W C) P + C = W D) P + C < W
12)
Answer: C
13) If you swing a bucket of water fast enough in a vertical circle, at the highest point the
water does not spill out because an outward force balances the pull of gravity on the
water.
A) True B) False
13)
Answer: B
6
14) A string is attached to the rear-view mirror of a car. A ball is hanging at the other end
of the string. The car is driving around in a circle, at a constant speed. Which of the
following lists gives all of the forces directly acting on the ball?
A) tension
B) tension, gravity, and the centripetal force
C) tension, gravity, the centripetal force, and friction
D) tension and gravity
14)
Answer: D
15) Suppose a highway curve is properly banked to eliminate friction for a speed of 45
mph. If your tires were bald and you wanted to avoid sliding on the road, you would
have to drive
A) at exactly 45 mph.
B) somewhat above 45 mph.
C) somewhat below 45 mph.
15)
Answer: A
16) When a parachutist jumps from an airplane, he eventually reaches a constant speed,
called the terminal speed. Once he has reached terminal speed
A) the force of air drag on him is equal to his weight.
B) the force of air drag on him is equal to zero.
C) the force of air drag on him is equal to g.
D) his acceleration is equal to g.
E) his speed is equal to g.
16)
Answer: A
17) Suppose the force of the air drag on an object is proportional to the speed of the object
and in the direction opposite the object’s velocity. If you throw an object upward, the
magnitude of its acceleration is greatest
A) at the top of its trajectory.
B) right after the object is released.
C) The acceleration of the object is the same throughout the entire trajectory.
17)
Answer: B
18) A 60.0-kg person rides in an elevator while standing on a scale. The scale reads 400 N.
The acceleration of the elevator is closest to
A) 6.67 m/s2 downward.
B) 6.67 m/s2 upward.
C) 3.13 m/s2 downward.
D) 9.80 m/s2 downward.
E) zero.
18)
Answer: C
7
19) A 60.0-kg person rides in elevator while standing on a scale. The elevator is traveling
downward but slowing down at a rate of 2.00 m/s2. The reading on the scale is closest
to
A) 469 N. B) 708 N. C) 120 N. D) 589 N. E) 349 N.
19)
Answer: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
20) Two objects are connected by a very light flexible string as shown in the figure,
where M = 0.60 kg and m = 0.40 kg. You can ignore friction and the mass of the
pulley.
(a) Draw free-body diagrams for each object.
(b) Calculate the magnitude of the acceleration of each object.
(c) Calculate the tension in the string.
20)
Answer: (a) The force of gravity acts downward and tension acts upward on each
object.
(b) 2.0 m/s2
(c) 4.7 N
8
21) Three boxes in contact 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 box in the center. A force
of 50 N pushes on the 5.0-kg box, which pushes against the other two boxes.
(a) Draw the free-body diagrams for each of the boxes.
(b) What magnitude force does the 3.0-kg box exert on the 5.0-kg box?
(c) What magnitude force does the 3.0-kg box exert on the 2.0-kg box?
21)
Answer: (a) The following forces act on the 5.0-kg box: the force due to gravity,
normal force, contact force between 5.0-kg mass and 3.0-kg mass, the
force of 50 N pushing on the box. The following forces act on the 3.0-kg
box: the force due to gravity, normal force, contact force between the
5.0-kg box and the 3.0-kg box, the contact force between the 3.0-kg box
and the 2.0-kg box. The following forces act on the 2.0-kg box: the force
due to gravity, normal force, contact force between the 3.0-kg box and the
2.0-kg box.
(b) 25 N
(c) 10 N
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
22) The figure shows a 100-kg block being released from rest from a height of 1.0 m. It
then takes it 0.90 s to reach the floor. What is the mass m of the other block? The pulley
has no appreciable mass or friction.
A) 42 kg B) 54 kg C) 60 kg D) 48 kg
22)
Answer: C
9
23) A wooden block A of mass 4.0 kg slides on a frictionless table when pulled using a
massless string and pulley array by a hanging box B of mass 5.0 kg, as shown in the
figure. What is the acceleration of block A as it slides on the frictionless table? Hint:
Think carefully about the acceleration constraint.
A) 3.5 m/s2 B) 3.1 m/s2 C) 4.1 m/s2 D) 2.7 m/s2
23)
Answer: C
24) The figure shows two 1.0 kg-blocks connected by a rope. A second rope hangs beneath
the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated
upward at 2.3 m/s2 by force F . What is the tension at the top end of rope 1?
A) 15 N B) 3.5 N C) 2.9 N D) 18 N
24)
Answer: D
10
25) A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface
as shown in the figure. The 6.00-kg block is being pushed by a horizontal 20.0-N force
as shown. What is the magnitude of the force that the 6.00-kg block exerts on the
4.00-kg block?
A) 4.00 N B) 6.00 N C) 8.00 N D) 20.0 N E) 10.0 N
25)
Answer: C
26) Three objects are connected by massless wires over a massless frictionless pulley as
shown in the figure. The tension in the wire connecting the 10.0-kg and 15.0-kg objects
is measured to be 133 N. What is the mass M?
A) 95.0 kg B) 52.8 kg C) 35.0 kg D) 8.33 kg E) 33.9 kg
26)
Answer: B
11
27) Three objects are connected by massless wires over a massless frictionless pulley as
shown in the figure. The tension in the wire connecting the 10.0-kg and 15.0-kg objects
is measured to be 133 N. What is the tension in wire A?
A) 87.5 N B) 333 N C) 245 N D) 280 N E) 517 N
27)
Answer: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
28) A 20.0-N box rests on a 50.0-N box on a perfectly smooth horizontal floor.
When a horizontal 15.0-N pull to the right is exerted on the lower box (see
figure), both boxes move together. Find the magnitude and direction of the net
external force on the upper box.
28)
Answer: 4.29 N to the right
12
29) A block is given a very brief push up a 20.0° frictionless incline to give it an
initial speed of 12.0 m/s.
(a) How far along the surface of the plane does the block slide before coming to
rest?
(b) How much time does it take to return to its starting position?
29)
Answer: (a) 21.5 m (b) 7.16 s
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
30) A child on a sled starts from rest at the top of a 15° slope. If the trip to the bottom takes
15.2 s how long is the slope? Assume that frictional forces may be neglected.
A) 586 m B) 147 m C) 293 m D) 1130 m
30)
Answer: C
31) A system comprising blocks, a light frictionless pulley, a frictionless incline, and
connecting ropes is shown in the figure. The 9.0-kg block accelerates downward when
the system is released from rest. The tension in the rope connecting the 6.0-kg block
and the 4.0-kg block is closest to
A) 39 N. B) 30 N. C) 33 N. D) 42 N. E) 36 N.
31)
Answer: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
32) A 50.0-kg box rests on a horizontal surface. The coefficient of static friction
between the box and the surface is 0.300 and the coefficient of kinetic friction
is 0.200. What is the friction force on the box if
(a) a horizontal 140-N push is applied to it?
(b) a horizontal 175-N push is applied to it?
32)
Answer: (a) 140 N (b) 98.0 N
13
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
33) A 4.00-kg block rests between the floor and a 3.00-kg block as shown in the figure.
The 3.00-kg block is tied to a wall by a horizontal rope. If the coefficient of static
friction is 0.800 between each pair of surfaces in contact, what horizontal force F must
be applied to the 4.00-kg block to make it move?
A) 16.2 N B) 21.1 N C) 54.9 N D) 78.4 N E) 23.5 N
33)
Answer: D
34) A 150-N box is being pulled horizontally in a wagon accelerating uniformly at
3.00 m/s2. The box does not move relative to the wagon, the coefficient of static
friction between the box and the wagon’s surface is 0.600, and the coefficient of kinetic
friction is 0.400. The friction force on this box is closest to
A) 60.0 N. B) 45.9 N. C) 90.0 N. D) 450 N.
34)
Answer: B
35) In a shuffleboard game, the puck slides a total of 12 m before coming to rest. If the
coefficient of kinetic friction between the puck and the horizontal board is 0.28, what
was the initial speed of the puck?
A) 29.0 m/s B) 6.5 m/s C) 7.3 m/s D) 8.1 m/s
35)
Answer: D
36) A driver in a 1000 kg car traveling at 20 m/s slams on the brakes and skids to a stop. If
the coefficient of friction between the tires and the horizontal road is 0.80, how long
will the skid marks be?
A) 33 m B) 24 m C) 21 m D) 26 m
36)
Answer: D
37) Jason takes off from rest across level water on his jet-powered skis. The combined
mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). The skis have a
thrust of 200 N and a coefficient of kinetic friction on water of 0.10. Unfortunately, the
skis run out of fuel after only 48 s. What is Jason’s top speed?
A) 130 m/s B) 13 m/s C) 81 m/s D) 48 m/s
37)
Answer: C
14
38) Jason takes off from rest across level water on his jet-powered skis. The combined
mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). The skis have a
thrust of 200 N and a coefficient of kinetic friction on water of 0.10. Unfortunately, the
skis run out of fuel after only 67 s. How far has Jason traveled when he finally coasts to
a stop?
A) 3800 m B) 5400 m C) 10,000 m D) 7600 m
38)
Answer: C
39) Kieran takes off from rest down a 50 m high, 10° slope on his jet-powered skis. The
skis have a thrust of 280 N parallel to the surface of the slope. The combined mass of
skis and Kieran is 50 kg (the fuel mass is negligible). Kieran’s speed at the bottom is 40
m/s. What is the coefficient of kinetic friction of his skis on snow?
A) 0.29 B) 0.47 C) 0.23 D) 0.58
39)
Answer: B
40) A factory robot drops a 10 kg computer onto a conveyor belt running at 3.1 m/s. The
materials are such that μs = 0.50 and μk = 0.30 between the belt and the computer. How
far is the computer dragged before it is riding smoothly on the belt?
A) 3.0 m B) 1.6 m C) 2.3 m D) 0.98 m
40)
Answer: B
41) You push downward on a box at an angle 25° below the horizontal with a force of
750 N. If the box is on a flat horizontal surface for which the coefficient of static
friction with the box is 0.76, what is the mass of the heaviest box you will be able to
move?
A) 59 kg B) 82 kg C) 68 kg D) 54 kg
41)
Answer: A
42) A person is dragging a packing crate of mass 100 kg across a rough horizontal floor
where the coefficient of kinetic friction is 0.400. He exerts a force F sufficient to
accelerate the crate forward. At what angle above horizontal should his pulling force be
directed in order to achieve the maximum acceleration?
A) 27.7° B) 45° C) 30° D) 21.8° E) 34.5°
42)
Answer: D
43) A packing crate rests on a horizontal surface. It is acted on by three horizontal forces:
600 N to the left, 200 N to the right, and friction. The weight of the crate is 400 N. If
the 600-N force is removed, the resultant force acting on the crate is
A) 200 N to the right.
B) 200 N to the left.
C) 400 N to the left.
D) zero.
E) impossible to determine from the information given.
43)
Answer: D
15
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
44) A pickup truck is moving at 25 m/s with a toolbox of mass m resting on the bed
of the truck 2.5 m behind the cab. Suddenly the brakes are applied, causing the
toolbox to slide, and the truck comes to a stop in 4.7 s. The coefficient of
kinetic friction between the toolbox and the bed of the truck is 0.28. After the
brakes are applied, how much time elapses before the toolbox strikes the cab?
44)
Answer: 1.4 s
45) Two boxes are connected by a weightless cord running over a very light
frictionless pulley as shown in the figure. Box A, of mass 8.0 kg, is initially at
rest on the top of the table. The coefficient of kinetic friction between box A
and the table is 0.10. Box B has a mass of 15.0 kg, and the system begins to
move just after it is released.
(a) Draw the free-body diagrams for each of the boxes, identifying all of the
forces acting on each one.
(b) Calculate the acceleration of each box.
(c) What is the tension in the cord?
45)
Answer: (a) Box A is acted on by the downward force of gravity, the upward
normal force due to the table top, the tension in the string toward the
right, and the force of friction due to the table top toward the left. Box B
is acted on by the downward force of gravity and the upward tension of the
string.
(b) 6.1 m/s2
(c) 56 N
16
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
46) A rope pulls on the lower block in the figure with a tension force of 20 N. The
coefficient of kinetic friction between the lower block and the surface is 0.16. The
coefficient of kinetic friction between the lower block and the upper block is also 0.16.
The pulley has no appreciable mass or friction. What is the acceleration of the 2.0 kg
block?
A) 9.2 m/s2 B) 8.4 m/s2 C) 5.1 m/s2 D) 4.1 m/s2
46)
Answer: D
47) Three objects are connected as shown in the figure. The strings and frictionless pulleys
have negligible masses, and the coefficient of kinetic friction between the 2.0-kg block
and the table is 0.25. What is the acceleration of the 2.0-kg block?
A) 4.0 m/s2 B) 2.5 m/s2 C) 1.7 m/s2 D) 3.2 m/s2
47)
Answer: B
17
48) A system comprised blocks, a light frictionless pulley, and connecting ropes is shown
in the figure. The 9.0-kg block is on a perfectly smooth horizontal table. The surfaces
of the 12-kg block are rough, with μk = 0.30 between the block and the table. If the
5.0-kg block accelerates downward when it is released, find its acceleration.
A) 1.0
m/s2
B) 1.6
m/s2
C) 1.2
m/s2
D) 1.8
m/s2
E) 1.4
m/s2
48)
Answer: A
49) Block A of mass 5.0 kg and block X are attached to a rope which passes over a pulley,
as shown in the figure. An 80-N force P is applied horizontally to block A, keeping it
in contact with a rough vertical face. The coefficients of static and kinetic friction
between the wall and block A are μs = 0.40 and μk = 0.30. The pulley is light and
frictionless. The mass of block X is adjusted until block A moves upward with an
acceleration of 1.6 m/s2. What is the mass of block X?
A) 9.3 kg B) 8.7 kg C) 8.1 kg D) 9.9 kg E) 7.5 kg
49)
Answer: D
18
50) In the figure, two wooden blocks each of 0.30 kg mass are connected by a string that
passes over a very light frictionless pulley. One block slides on a horizontal table,
while the other hangs suspended by the string, as shown in the figure. At time t = 0, the
suspended block is 0.80 m over the floor, and the blocks are released from rest. After
2.5 s, the suspended block reaches the floor. What is the coefficient of kinetic friction
between the table and the sliding block?
A) 0.65 B) 0.52 C) 0.84 D) 0.95 E) 0.35
50)
Answer: D
19
51) A 4.00-kg box sits atop a 10.0-kg box on a horizontal table. The coefficient of kinetic
friction between the two boxes and between the lower box and the table is 0.600, while
the coefficient of static friction between these same surfaces is 0.800. A horizontal pull
to the right is exerted on the lower box, as shown in the figure, and the boxes move
together. What is the friction force on the UPPER box?
A) 31.4 N to the left
B) 19.3 N to the right
C) 23.5 N to the right
D) 19.3 N to the left
E) 31.4 N to the right
51)
Answer: B
52) A 6.0 kg box slides down an inclined plane that makes an angle of 39° with the
horizontal. If the coefficient of kinetic friction is 0.19, at what rate does the box
accelerate down the slope?
A) 6.2 m/s2 B) 4.7 m/s2 C) 5.5 m/s2 D) 5.2 m/s2
52)
Answer: B
53) A 200 g hockey puck is launched up a metal ramp that is inclined at a 30° angle. The
coefficients of static and kinetic friction between the hockey puck and the metal ramp
are μs = 0.40 and μk = 0.30, respectively. The puck’s initial speed is 63 m/s. What
vertical height does the puck reach above its starting point?
A) 66 m B) 270 m C) 130 m D) 200 m
53)
Answer: C
54) A 200 g hockey puck is launched up a metal ramp that is inclined at a 30° angle. The
coefficients of static and kinetic friction between the hockey puck and the metal ramp
are
μs = 0.40 and μk = 0.30, respectively. The puck’s initial speed is 4.9 m/s. What speed
does it have when it slides back down to its starting point?
A) 3.5 m/s B) 2.8 m/s C) 4.2 m/s D) 4.9 m/s
54)
Answer: B
20
55) A 4.00-kg block rests on a 30.0° incline as shown in the figure. If the coefficient of
static friction between the block and the incline is 0.700, what magnitude horizontal
force F must act on the block to start it moving up the incline?
A) 84.0 N B) 54.7 N C) 51.1 N D) 76.4 N E) 34.0 N
55)
Answer: A
56) A box is sliding down an incline tilted at a 12.0° angle above horizontal. The box is
initially sliding down the incline at a speed of 1.50 m/s. The coefficient of kinetic
friction between the box and the incline is 0.340. How far does the box slide down the
incline before coming to rest?
A) 2.33 m
B) 0.720 m
C) 1.78 m
D) 0.920 m
E) The box does not stop. It accelerates down the plane.
56)
Answer: D
57) A 50.0-kg block is being pulled up a 16.0° slope by a force of 250 N which is parallel
to the slope. The coefficient of kinetic friction between the block and the slope is
0.200. What is the magnitude of the acceleration of the block?
A) 0.983 m/s2
B) 0.260 m/s2
C) 0.412 m/s2
D) 0.158 m/s2
E) 0.528 m/s2
57)
Answer: C
21
58) Two blocks are connected by a string that goes over an ideal pulley as shown in the
figure. Block A has a mass of 3.00 kg and can slide over a rough plane inclined 30.0° to
the horizontal. The coefficient of kinetic friction between block A and the plane is
0.400. Block B has a mass of 2.77 kg. What is the acceleration of the blocks?
A) 5.35 m/s2
B) 3.12 m/s2
C) 0.392 m/s2
D) 1.96 m/s2
E) 0.00 m/s2
58)
Answer: C
59) The figure shows two packages that start sliding down a 20° ramp from rest a distance
d = 6.6 m along the ramp from the bottom. Package A has a mass of 5.0 kg and a
coefficient of kinetic friction 0.20 between it and the ramp. Package B has a mass of 10
kg and a coefficient of kinetic friction 0.15 between it and the ramp. How long does it
take package A to reach the bottom?
A) 3.0 s B) 3.5 s C) 2.7 s D) 3.2 s
59)
Answer: C
22
60) In the figure, a T-bar ski tow pulls a skier up a hill inclined at 10° above horizontal.
The skier starts from rest and is pulled by a cable that exerts a tension T at an angle of
30° above the surface of the hill. The mass of the skier is 60 kg and the effective
coefficient of kinetic friction between the skis and the snow is 0.100. What is the
maximum tension in the cable if the starting acceleration is not to exceed 0.400 g?
A) 366 N B) 246 N C) 431 N D) 187 N E) 535 N
60)
Answer: C
61) A 250-kg crate is on a rough ramp, inclined at 30° above the horizontal. The coefficient
of kinetic friction between the crate and ramp is 0.22. A horizontal force of 5000 N is
applied to the crate, pushing it up the ramp. What is the acceleration of the crate?
A) 12 m/s2 B) 10 m/s2 C) 3.4
m/s2
D) 13 m/s2 E) 8.4
m/s2
61)
Answer: E
23
62) Two weights are connected by a massless wire and pulled upward with a constant
speed of 1.50 m/s by a vertical pull P. The tension in the wire is T (see figure). P is
closest to
A) 25 N. B) 187.5
N.
C) 245 N. D) 125 N. E) 1225 N.
62)
Answer: D
63) The figure shows two forces acting at right angles on an object. They have magnitudes
F1 = 6.3 N and F2 = 2.1 N. What third force will cause the object to be in equilibrium
(acceleration equals zero)?
A) 4.2 N at 162° counterclockwise from F 1
B) 6.6 N at 108° counterclockwise from F 1
C) 6.6 N at 162° counterclockwise from F 1
D) 4.2 N at 108° counterclockwise from F 1
63)
Answer: C
24
64) The figure shows two forces, each of magnitude 4.6 N, acting on an object. The angle
between these forces is 40°, and they make equal angles above and below the
horizontal. What third force will cause the object to be in equilibrium (acceleration
equals zero)?
A) 4.3 N pointing to the right B) 8.6 N pointing to the right
C) 7.0 N pointing to the right D) 3.5 N pointing to the right
64)
Answer: B
65) A traffic light weighing 100 N is supported by two ropes as shown in the figure. The
tensions in the ropes are closest to
A) 83 N. B) 50 N. C) 66 N. D) 56 N. E) 63 N.
65)
Answer: A
25
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
66) Two blocks are connected by a string that goes over an ideal pulley as shown in
the figure and pulls on block A parallel to the surface of the plane. Block A has
a mass of 3.00 kg and can slide along a rough plane inclined 30.0° to the
horizontal. The coefficient of static friction between block A and the plane is
0.400. What mass should block B have in order to start block A sliding up the
plane?
66)
Answer: 2.54 kg
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
67) The figure shows a 2000 kg cable car descending a high hill. A counterweight of mass
1800 kg on the other side of the hill aids the brakes in controlling the cable car’s speed.
The rolling friction of both the cable car and the counterweight are negligible. How
much braking force does the cable car need to descend at constant speed?
A) 3800 N B) 980 N C) 2900 N D) 2000 N
67)
Answer: A
26
68) A system of blocks and a frictionless pulley is shown in the figure. Block A has a mass
of 2.0 kg and is on a rough horizontal surface for which μs = 0.40 between the surface
and block A. The rope pulls horizontally on block A. Block C has a mass of 1.0 kg. An
external force P = 23.0 N, applied vertically to block A, maintains the system at rest as
shown in the figure. What is the friction force on block A?
A) 5.7 N B) 6.3 N C) 6.9 N D) 7.5 N E) 5.1 N
68)
Answer: B
69) In the figure, a block of mass M hangs at rest. The rope that is fastened to the wall is
horizontal and has a tension off 52 N. The rope that is fastened to the ceiling has a
tension of 91 N,and makes an angle θ with the ceiling. What is the angle θ?
A) 30° B) 63° C) 45° D) 55° E) 35°
69)
Answer: D
27
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
70) A 1520-N crate is to be held in place on a ramp that rises at 30.0° above the
horizontal (see figure). The massless rope attached to the crate makes a 22.0°
angle above the surface of the ramp. The coefficients of friction between the
crate and the surface of the ramp are μk = 0.450 and μs = 0.650. The pulley has
no appreciable mass or friction. What is the MAXIMUM weight w that can be
used to hold this crate stationary on the ramp?
70)
Answer: 1380 N
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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
71) Block A of mass 8.0 kg and block X are attached to a rope that passes over a pulley. A
50-N force P is applied horizontally to block A, keeping it in contact with a rough
vertical face. The coefficients of static and kinetic friction between the wall and block
A are μs = 0.40 and μk = 0.30. The pulley is light and frictionless. In the figure, the
mass of block X is adjusted until block A descends at constant velocity of 4.75 cm/s
when it is set into motion. What is the mass of block X?
A) 7.2 kg B) 6.5 kg C) 8.0 kg D) 9.5 kg E) 8.8 kg
71)
Answer: B
72) A 23 kg mass is connected to a nail on a frictionless table by a massless string 1.3 m
long. There is no appreciable friction between the nail and the string. If the tension in
the string is 51 N while the mass moves in a uniform circle on the table, how long does
it take for the mass to make one complete revolution?
A) 5.2 s B) 4.8 s C) 4.5 s D) 3.8 s
72)
Answer: B
73) A car travels at a steady 40.0 m/s around a horizontal curve of radius 200 m. What is
the minimum coefficient of static friction between the road and the car’s tires that will
allow the car to travel at this speed without sliding?
A) 0.816 B) 0.662 C) 0.736 D) 0.952 E) 1.23
73)
Answer: A
74) A car enters a 300-m radius horizontal curve on a rainy day when the coefficient of
static friction between its tires and the road is 0.600. What is the maximum speed at
which the car can travel around this curve without sliding?
A) 42.0
m/s
B) 24.8
m/s
C) 29.6
m/s
D) 33.1
m/s
E) 37.9
m/s
74)
Answer: A
29
75) A car drives over a hilltop that has a radius of curvature 0.120 km at the top of the hill.
At what speed would the car be traveling when it tires just barely lose contact with the
road when the car is at the top of the hill?
A) 41.8
m/s
B) 27.6
m/s
C) 45.5
m/s
D) 34.3
m/s
E) 22.2
m/s
75)
Answer: D
76) A 1000-kg car is slowly picking up speed as it goes around a horizontal curve whose
radius is 100 m. The coefficient of static friction between the tires and the road is
0.350. At what speed will the car begin to skid sideways?
A) 35.0
m/s
B) 34.3
m/s
C) 9.25
m/s
D) 18.5
m/s
E) 23.6
m/s
76)
Answer: D
77) A 600-kg car is going around a banked curve with a radius of 110 m at a speed of
24.5 m/s. What is the appropriate banking angle so that the car stays on its path without
the assistance of friction?
A) 29.1° B) 56.2° C) 33.8° D) 13.5° E) 60.9°
77)
Answer: A
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
78) A 600-kg car traveling at 24.5 m/s is going around a curve having a radius of
120 m that is banked at an angle of 20°.
(a) Is the curve properly banked for the car’s speed?
(b) What is the minimum coefficient of static friction required between the road
and the car’s tires so the car does not skid?
78)
Answer: (a) No (b) 0.12
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
79) A 600-kg car traveling at 30.0 m/s is going around a curve having a radius of 120 m
that is banked at an angle of 25.0°. The coefficient of static friction between the car’s
tires and the road is 0.300. What is the magnitude of the force exerted by friction on
the car?
A) 795 N B) 1590 N C) 3430 N D) 7820 N E) 7240 N
79)
Answer: B
80) Engineers are designing a curved section of a highway. If the radius of curvature of the
curve is 194 m, at what angle should the curve be banked so that a car traveling at 29.0
m/s will stay on the road without the aid of frictional forces?
A) 21.0° B) 16.7° C) 26.1° D) 23.9°
80)
Answer: D
30
81) The figure shows two wires tied to a 3.3 kg sphere that revolves in a horizontal circle at
constant speed. At this particular speed the tension is the SAME in both wires. What is
the tension?
A) 22 N B) 24 N C) 32 N D) 44 N
81)
Answer: B
31
82) The figure shows two wires that are tied to a 710 g mass that revolves in a horizontal
circle at a constant speed of 7.5 m/s. What is the tension in the upper wire?
A) 27 N B) 20 N C) 34 N D) 41 N
82)
Answer: C
83) Future space stations will create an artificial gravity by rotating. Consider a cylindrical
space station 390 m diameter rotating about its central axis. Astronauts walk on the
inside surface of the space station. What rotation period will provide “normal” gravity?
A) 28 s B) 4.4 s C) 40 s D) 6.3 s
83)
Answer: A
84) A new roller coaster contains a loop-the-loop in which the car and rider are completely
upside down. If the radius of the loop is 13.2 m, with what minimum speed must the
car traverse the loop so that the rider does not fall out while upside down at the top?
Assume the rider is not strapped to the car.
A) 14.9 m/s B) 12.5 m/s C) 10.1 m/s D) 11.4 m/s
84)
Answer: D
32
85) A ball of mass 5.0 kg is suspended by two wires from a horizontal arm that is attached
to a vertical shaft, as shown in the figure. The shaft is in uniform rotation about its axis.
The rate of rotation is adjusted until the tensions in the two wires are EQUAL. At that
speed, the radial acceleration of the ball is closest to
A) 4.9
m/s2.
B) 5.9
m/s2.
C) 7.9
m/s2.
D) 9.9
m/s2.
E) 6.9
m/s2.
85)
Answer: A
86) A roadway for stunt drivers is designed for racecars moving at a speed of 40 m/s. A
curved section of the roadway is a circular arc of 230 m radius. The roadway is banked
so that a vehicle can go around the curve with the friction force from the road equal to
zero. At what angle is the roadway banked?
A) 37° B) 31° C) 29° D) 35° E) 33°
86)
Answer: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
87) A person on a sled coasts down a hill and then goes over a slight rise with speed
2.7 m/s. The top of this rise can be modeled as a circle of radius 4.1 m. The sled
and occupant have a combined mass of 110 kg. If the coefficient of kinetic
friction between the snow and the sled is 0.10, what friction force is exerted on
the sled by the snow as the sled goes over the top of the rise?
87)
Answer: 88 N
88) A Ferris wheel has diameter of 10 m and makes one revolution in 8.0 seconds.
A person weighing 670 N is sitting on one of the benches attached at the rim of
the wheel. What is the apparent weight (that is, the normal force exerted on her
by the bench) of the person as she passes through the highest point of her
motion?
88)
Answer: 460 N
33
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
89) The magnitude of the drag force of air resistance on a certain 20.0-kg object is
proportional to its speed. If the object has a terminal speed of 80.0 m/s, what is the
magnitude of the drag force on the object when it is falling with a speed of 30.0 m/s?
A) 7.50 N B) 196 N C) 42.7 N D) 15.0 N E) 73.5 N
89)
Answer: E
90) A 30.0-kg object experiences a drag force due to air resistance with a magnitude
proportional to the square of its speed. The object falls with an acceleration of 4.00
m/s2 downward when it is falling downward at 70.0 m/s. What is its terminal speed?
A) 110 m/s B) 172 m/s C) 91.0
m/s
D) 157 m/s E) 108 m/s
90)
Answer: C
91) A ship is being pulled through a harbor at constant velocity by two tugboats as shown
in the figure. The lines attached to the two tugboats have the same tension of 200,000
N. Each line makes an angle of 28.0° with the direction the ship is being towed. What is
the magnitude of the drag force due to the water on the ship?
A) 177 × 105 N
B) 93.9 × 104 N
C) 3.53 × 105 N
D) zero
E) 1.88 × 105 N
91)
Answer: C
92) A 1.20-kg ball is hanging from the end of a rope. The rope hangs at an angle 25.0°
from the vertical when a 15.0 m/s horizontal wind is blowing. If the wind’s force on the
rope is negligible, what drag force does the wind exert on the ball?
A) 32.3 N B) 11.8 N C) 5.48 N D) 3.68 N E) 24.1 N
92)
Answer: C
34
93) An 80.0-kg object is falling and experiences a drag force due to air resistance. The
magnitude of this drag force depends on its speed, v, and obeys the equation
Fdrag = (12.0 N • s/m)v + (4.00 N • s2/m2)v2. What is the terminal speed of this
object?
A) 34.2
m/s
B) 72.2
m/s
C) 47.3
m/s
D) 12.6
m/s
E) 6.45
m/s
93)
Answer: D
94) An object weighing 4.00 N falls from rest subject to a frictional drag force given by
Fdrag = bv2, where v is the speed of the object and b = 3.00 N • s2/m2. What terminal
speed will this object approach?
A) 0.75
m/s
B) 1.78
m/s
C) 1.15
m/s
D) 2.25
m/s
E) 3.42
m/s
94)
Answer: C
95) The figure shows two forces acting on an object, with magnitudes F1 = 78 N and
F2 = 26 N.What third force will cause the object to be in equilibrium (acceleration equals
zero)?
A) 82 N pointing up B) 52 N pointing down
C) 52 N pointing up D) 82 N pointing down
95)
Answer: B
35

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