Deck 6: Applications of Newtons Laws

Question 1

A body moving with constant speed cannot be accelerating.

Answer 1

False

Question 2

For uniform circular motion, the velocity and acceleration vectors are perpendicular to each other at every point in the path.

Answer 2

True

Question 3

An airplane is flying with constant speed along a horizontal circle. Is the direction of its acceleration constant?

Answer 3

No.The acceleration is directed towards the center of the circle,so the acceleration vector rotates as the body rotates.

Question 4

Why does a cyclist tilt her bicycle on a curve?

Question 5

When a curve is properly banked a passenger in a car traveling on it at the designed speed does not feel a lateral force.

Question 6

You are driving your car and set your sunglasses on the dashboard. When you make a left turn, the sunglasses go sliding off to the right. Explain.

Question 7

You are driving in your car with a sack of groceries in the seat next to you. You see a light change and you slow down and the sack remains on the seat. Suddenly the car in front of you slams on the brakes, and you are forced to brake harder. The groceries slide off the seat. Explain what happened.

Question 8

An ideal pulley changes the direction of the tension in a string without changing its magnitude.

Question 9

Is it possible for an object moving with a constant speed to accelerate?
Explain.

Question 10

An object moving along a curved path with constant speed does not have a net force acting on it.

Question 11

The force fo static friction between two surfaces is parallel to the surface of contact, and in in the direction that opposes relative motion.

Question 12

The force of kinetic friction between two surfaces is dependent on the relative speed of the two surfaces.

Question 13

State the condition for an object to be in translational equilibrium.

Question 14

The force of kinetic friction between two surfaces is independent of the area of contact between the surfaces.

Question 15

The force of static friction between two surfaces is independent of the area of contact between the surfaces.

Question 16

The stretch of a spring and the force it exerts are inversely proportional.

Question 17

When an object is in translational equilibrium, the net force acting on the object is non-zero.

Question 18

The banking angle for a properly banked curve does not depend on the mass of the car going over it.

Question 19

A net horizontal force is required for a body to move in a horizontal circle.

Question 20

The coefficient of static friction is always larger than the coefficient of kinetic friction.

Question 21

FIGURE 6-1
In Figure 6-1, the block of mass m is at rest on an inclined plane that makes an angle θ with the horizontal. The normal force F acting on the block must be such that

A) F > mg.
B) F > mg cosθ.
C) F > mg sinθ.
D) F = mg cosθ.
E) F = mg sinθ.

Question 22

What type of acceleration does an object moving with constant speed in a circular path experience?

A) free fall.
B) terminal acceleration.
C) constant acceleration.
D) linear acceleration.
E) centripetal acceleration.

Question 23

FIGURE 6-3
Compare the two situations shown in Figure 6-3. On the left (A), James is holding the rope and keeping the bucket at rest. On the right (B), James ties the rope to the bucket so that it keeps the bucket at rest. In both cases the bucket contains the same quantity of water. In what case is the tension in the rope higher?

A) left
B) right
C) It is the same in both cases.
D) We need more data to answer.

Question 24

Its more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because

A) The normal force is greater when the carton is at rest.
B) μ_s < μ_k.
C) Initially, the normal force is not perpendicular to the applied force.
D) μ_k < μ_s.
E) μ_s = μ_k.

Question 25

FIGURE 6-1
In Figure 6-1, the block of mass m is at rest on an inclined plane that makes an angle θ with the horizontal. The force of static friction f must be such that

A) f > mg.
B) f > mg cosθ.
C) f > mg sinθ.
D) f = mg cosθ.
E) f = mg sinθ.

Question 26

Consider a particle moving with constant speed such that its acceleration of constant magnitude is always perpendicular to its velocity.

A) It is moving in a straight line.
B) It is moving in a circle.
C) It is moving in a parabola.
D) It is moving in a hyperbola.
E) None of the above is definitely true all of the time.

Question 27

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is

A) static friction.
B) kinetic friction.
C) a combination of static and kinetic friction.
D) neither static nor kinetic friction, but some other type of friction.
E) It is impossible to tell what type of friction acts in this situation.

Question 28

When a car goes around a curve, it has a tendency to skid outwards. Is the frictional force between the tires and the ground that keeps the car from skidding kinetic or static?

A) kinetic
B) static

Question 29

When an object experiences uniform circular motion, the direction of the acceleration is

A) in the same direction as the velocity vector.
B) in the opposite direction of the velocity vector.
C) is directed toward the center of the circular path.
D) is directed away from the center of the circular path.
E) depends on the speed of the object.

Question 30

When an object experiences uniform circular motion, the direction of the net force is

A) in the same direction as the motion of the object.
B) in the opposite direction of the motion of the object.
C) is directed toward the center of the circular path.
D) is directed away from the center of the circular path.
E) is dependent on the speed of the object.

Question 31

For an object that travels at a fixed speed along a circular path, the acceleration of the object is

A) larger in magnitude the smaller the radius of the circle.
B) in the same direction as the velocity of the object.
C) smaller in magnitude the smaller the radius of the circle.
D) in the opposite direction of the velocity of the object.
E) zero.

Question 32

A flatbed truck is carrying a crate along a level road. The coefficient of static friction between the load and the bed is 0.40. The truck accelerates forward and the crate stays in its place on the truck bed. In what direction is the force that the bed exerts on the crate?

A) forward
B) backward
C) toward the center of the road
D) There is no frictional force because the crate does not move with respect to the bed.
E) There is not enough information to answer this question.

Question 33

An object moves in a circular path at a constant speed. Compare the direction of the object's velocity and acceleration vectors.

A) Both vectors point in the same direction.
B) The vectors point in opposite directions.
C) The vectors are perpendicular.
D) The question is meaningless, since the displacement is zero.
E) The question is meaningless, since the acceleration is zero.

Question 34

A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that

A) a frictional force is acting on it.
B) a net downward force is acting on it.
C) a net upward force is acting on it.
D) it is not acted on by appreciable normal force.
E) it is not acted on by appreciable gravitational force.

Question 35

A roller coaster car is on a track that forms a circular loop in the vertical plane. If the car is to just maintain contact with track at the top of the loop, what is the minimum value for its centripetal acceleration at this point?

A) g downward
B) 0.5g downward
C) 2g downward
D) g upward
E) 2g upward

Question 36

If a car slows down with the wheels rolling, is the frictional force between the tires and the ground kinetic or static?

A) kinetic
B) static

Question 37

FIGURE 6-5
Two masses, m₁ and m₂, are connected to each other as shown in Figure 6-5. Mass m₁ slides without friction on the table surface. Both masses have acceleration of magnitude a as shown. How does the tension in the string compare to the weight, m₂ g, of mass m₂?

A) The tension is equal to m₂ g.
B) The tension is larger than m₂ g.
C) The tension is smaller than m₂ g.
D) It depends on m₁ being smaller than m₂.
E) It depends on m₁ being larger than m₂.

Question 38

FIGURE 6-2
In Figure 6-2 the scale at left is attached to the ceiling and a mass of 1.00 kg hangs from it. It reads 9.81 N. The identical scale at the right is connected by perfect strings passing over perfect pulleys to two 1.00 kg masses hanging vertically at the end of the strings. The scale at right reads

A) exactly 9.81 N.
B) more than 9.81 N, but not quite twice as much.
C) less than 9.81 N.
D) exactly 19.62 N.
E) more than 19.62 N.

Question 39

FIGURE 6-4
A 16-kg fish is weighed with two spring scales, each of negligible weight, as shown in Figure 6-4. What will be the readings on the scales?

A) The bottom scale will read 16 kg, and the top scale will read zero.
B) The sum of the two readings will be 32 kg.
C) The top scale will read 16 kg, and the bottom scale will read zero.
D) Each scale will show a reading greater than zero and less than 16 kg, but the sum of the two readings will be 16 kg.
E) Each scale will read 8 kg.

Question 40

FIGURE 6-6
Two identical masses are attached by a light string that passes over a small pulley, as shown in Figure 6-6. The table and the pulley are frictionless. The masses are moving

A) with an acceleration less than g.
B) at constant speed.
C) with an acceleration greater than g.
D) with an acceleration equal to g.
E) with an acceleration that cannot be determined without additional information.

Question 41

A flatbed truck is carrying a 20.0-kg crate up a sloping road inclined 15.0° above the horizontal. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place?

A) 0.625 m/s²
B) 1.25 m/s²
C) 2.50 m/s²
D) 3.16 m/s²
E) 6.33 m/s²

Question 42

FIGURE 6-7
A 30.0-kg load is being lifted with constant speed using the ideal pulley arrangement shown in Figure 6-7. What is the magnitude of the force F?

Question 43

A 50.0-kg box is being pulled along a horizontal surface by means of a rope that exerts a force of 250 N at an angle of 32.0° above the horizontal. The coefficient of kinetic friction between the box and the surface is 0.350. What is the acceleration of the box?

A) 0.638 m/s²
B) 1.74 m/s²
C) 3.16 m/s²
D) 6.31 m/s²
E) 8.53 m/s²

Question 44

A baseball player is running to second base at 5.03 m/s. When he is 4.80 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.180. What is his speed when he reaches the plate?

A) 4.47 m/s
B) 2.89 m/s
C) 1.96 m/s
D) 2.56 m/s
E) He stops before reaching the plate.

Question 45

A roller coaster car (mass = M) is on a track that forms a circular loop (radius = r) in the vertical plane. If the car is to just maintain contact with the track at the top of the loop, what is the minimum value for its speed at that point?

A) rg
B) 2rg
C) (rg)^1/2
D) (2rg)^1/2
E) (0.5rg)^1/2

Question 46

A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place?

A) 3.92 m/s²
B) 7.84 m/s²
C) 8.00 m/s²
D) 78.5 m/s²
E) 196 m/s²

Question 47

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A 140-N force is applied to the box. What is the frictional force on the box?

Question 48

FIGURE 6-8
Two masses are connected by a string which goes over an ideal pulley as shown in
Figure 6-8. 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 ramp?

Question 49

A flatbed truck is carrying a 20.0-kg crate down a sloping road inclined 15.0° below the horizontal. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place?

A) 1.25 m/s²
B) 0.625 m/s²
C) 2.50 m/s²
D) 3.16 m/s²
E) 6.33 m/s²

Question 50

FIGURE 6-7
A workman lowers a 30.0-kg load using the ideal pulley arrangement shown in Figure 6-7. He allows the rope to slide in his hands, thus exerting a downward force of 100 N on the rope. What is the acceleration of the load?

Question 51

A child pulls a 3.00-kg sled across level ground at constant velocity with a light rope that makes an angle 30.0° above horizontal. The tension in the rope is 5.00 N. Assuming the acceleration of gravity is 9.81 m/s², what is the coefficient of friction between the sled and the ground?

A) 0.161
B) 0.188
C) 0.0441
D) 0.0851
E) 0.103

Question 52

A policeman investigating an accident measures the skid marks left by a car. He determines that the distance between the point that the driver slammed on the brakes and the point where the car came to a stop was 28.0 m. From a reference manual he determines that the coefficient of kinetic friction between the tires and the road under the prevailing conditions was 0.300. How fast was the car going when the driver applied the brakes? (This car was not equipped with anti-lock brakes.)

A) 10.7 m/s
B) 12.8 m/s
C) 21.4 m/s
D) 32.9 m/s
E) 45.7 m/s

Question 53

A 60.0-kg mass person wishes to push a 120-kg mass box across a level floor. The coefficient of static friction between the person's shoes and the floor is 0.700. What is the maximum coefficient of static friction between the box and the floor such that the person can push horizontally on the box and cause it to start moving?

A) 0.333
B) 0.500
C) 0.350
D) 0.667
E) 0.700

Question 54

A 50.0-kg box is being pushed along a horizontal surface by a force of 250 N directed 28.0° below the horizontal. The coefficient of kinetic friction between the box and the surface is 0.300. What is the acceleration of the box?

A) 0.769 m/s²
B) 1.77 m/s²
C) 3.16 m/s²
D) 6.31 m/s²
E) 8.53 m/s²

Question 55

A 50.0-kg box is being pushed along a horizontal surface. The coefficient of kinetic friction between the box and the ground is 0.350. What horizontal force must be exerted on the box for it to accelerate at 1.20 m/s²?

A) 60.0 N
B) 116 N
C) 172 N
D) 232 N
E) 491 N

Question 56

A flatbed truck is carrying a 20.0-kg crate up a sloping road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place?

A) 0.381°
B) 13.1°
C) 21.8°
D) 23.6°
E) 66.4°

Question 57

FIGURE 6-7
A 30.0-kg load is being raised by a force of 180 N using the ideal pulley arrangement shown in Figure 6-7. What is the acceleration of the load?

Question 58

A 50.0-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the surface is 0.400. What is the force of friction on the box?

A) 31.9 N
B) 196 N
C) 217 N
D) 246 N
E) 616 N

Question 59

A 55.0-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.300. What horizontal force must be applied to the box for it to start sliding along the surface?

Question 60

The banking angle in a turn on the Olympic bobsled track is not constant, but increases upward from the horizontal. Coming around a turn, the bobsled team will intentionally "climb the wall," then go lower coming out of the turn. Why do they do this?

A) to give the team better control, because they are able to see ahead of the turn
B) to prevent the bobsled from turning over
C) to take the turn at a faster speed
D) to take the turn at a slower speed
E) to reduce the g-force on them

Question 61

Diff: 1 Var: 5 Page Ref: Sec. 6-2
A mass of 40.0 grams is attached to a vertical spring with a spring constant k = 20.0 N/m and lowered slowly until the spring stops stretching. How much does the spring stretch?

A) 0.00200 m
B) 0.0196 m
C) 0.0816 m
D) 0.800 m
E) 0.200 m

Question 62

FIGURE 6-11
Refer to Figure 6-11. Block A has a mass of 3.00 kg and rests on a smooth table and is connected to block B, which has a mass of 2.00 kg, after passing over an ideal pulley, as shown. Block B is released from rest. What is the acceleration of the masses?

A) 3.22 m/s²
B) 5.10 m/s²
C) 3.92 m/s²
D) 6.54 m/s²
E) 8.24 m/s²

Question 63

A 50.0-kg block is being pushed up a 15.0° slope by a force of 300 N which is directed 30.0° below the slope. The coefficient of kinetic friction between the block and the slope is 0.200. What is the acceleration of the block?

A) 0.164 m/s²
B) 0.967 m/s²
C) 1.20 m/s²
D) 2.20 m/s²
E) 0.528 m/s²

Question 64

FIGURE 6-9

-A 22.0-kg crate is pulled along a horizontal floor by the ideal arrangement shown in
Figure 6-9. The force F is 300 N. The coefficient of friction between the crate and the floor is 0.270. What is the acceleration of the crate?

A) 4.17 m/s²
B) 6.57 m/s²
C) 2.34 m/s²
D) 4.85 m/s²
E) 9.65 m/s²

Question 65

FIGURE 6-10
A 10-kg sign is held by two ropes as shown in Figure 6-10. What is the tension on rope A?

A) 44 N
B) 69 N
C) 72 N
D) 88 N
E) 98 N

Question 66

A 3.00-kg mass rests on the ground. It is attached to a string which goes vertically to and over an ideal pulley. A second mass is attached to the other end of the string and released. The 3.00-kg mass rises 50.0 cm in 1.00 s. How large was the other mass?

A) 3.67 kg
B) 4.29 kg
C) 6.83 kg
D) 7.15 kg
E) 7.34 kg

Question 67

FIGURE 6-11
Refer to Figure 6-11. Block A has a mass of 3.00 kg and rests on a smooth table and is connected to block B, which has a mass of 2.00 kg, after passing over an ideal pulley, as shown. Block B is released from rest. How long does it take block B to travel 80.0 cm?

A) 0.404 s
B) 0.494 s
C) 0.639 s
D) 0.785 s
E) 0.935 s

Question 68

A 50.0-kg block is being pulled up a 15.0° slope by a force of 300 N which is directed 30.0° above the slope. The coefficient of kinetic friction between the block and the slope is 0.200. What is the acceleration of the block?

A) 1.36 m/s²
B) 0.158 m/s²
C) 0.924 m/s²
D) 0.520 m/s²
E) 1.47 m/s²

Question 69

A 3.00-kg mass and a 5.00-kg mass hang vertically at the ends of a rope that goes over an ideal pulley. If the masses are released from rest, how long does it take for the 3.00-kg mass to rise by 1.00 m?

A) 0.407 s
B) 0.735 s
C) 0.815 s
D) 1.81 s
E) 0.903 s

Question 70

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 acceleration of the block?

A) 0.528 m/s²
B) 0.158 m/s²
C) 0.412 m/s²
D) 0.983 m/s²
E) 0.260 m/s²

Question 71

FIGURE 6-12
Two masses are connected by a string which goes over an ideal pulley as shown in Figure 6-12. Block A has a mass of 3.0 kg and can slide along a smooth plane inclined 30° to the horizontal. What is the mass of block B if the system is in equilibrium?

A) 1.5 kg
B) 3.0 kg
C) 2.6 kg
D) 3.5 kg
E) 6.0 kg

Question 72

A 50.0-kg block is being pulled up a 13.0° slope by a force of 250 N which is parallel to the slope, but the block does not slide up the slope. What is the minimum value of the coefficient of static friction required for this to happen?

A) 0.115
B) 0.566
C) 0.654
D) 0.359
E) 0.292

Question 73

A 3.00-kg mass and a 5.00-kg mass hang vertically at the ends of a rope that goes over an ideal pulley. If the masses are released, what is the resulting acceleration of the masses?

A) 0 m/s²
B) 3.68 m/s²
C) 2.45 m/s²
D) 4.90 m/s²
E) 6.13 m/s²

Question 74

A mass of 3.0 kg rests on a smooth surface inclined 34° above the horizontal. It is kept from sliding down the plane by a spring attached to a wall. The spring is aligned with the plane and has a spring constant of 120 N/m. How much does the spring stretch?

A) 360 cm
B) 240 cm
C) 14 cm
D) 24 cm
E) 36 cm

Question 75

A box slides down a 25.0° slope under its own weight. The coefficient of kinetic friction between the box and the slope is 0.350. What is the acceleration of the box?

A) 1.03 m/s²
B) 2.06 m/s²
C) 1.22 m/s²
D) 2.20 m/s²
E) 2.44 m/s²

Question 76

A tightrope walker with a mass of 60.0 kg stands at the center of a rope which was initially strung horizontally between two poles. His weight causes the rope to sag symmetrically, making an angle of 4.80° with the horizontal. What is the tension in the rope?

A) 359 N
B) 589 N
C) 1760 N
D) 2470 N
E) 3520 N

Question 77

FIGURE 6-10
A 10-kg sign is held by two ropes as shown in Figure 6-10. What is the tension on rope B?

A) 69 N
B) 44 N
C) 72 N
D) 88 N
E) 98 N

Question 78

FIGURE 6-11
Refer to Figure 6-11. Block A has a mass of 2.00 kg and rests on a rough table and is connected to block B, which has a mass of 3.00 kg, after passing over an ideal pulley, as shown. Block B is released from rest. The coefficient of kinetic friction between block A and the table is 0.300. What is the acceleration of the masses?

A) 3.92 m/s²
B) 0.981 m/s²
C) 4.71 m/s²
D) 5.89 m/s²
E) 6.54 m/s²

Question 79

A 50.0-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 26.0° below the horizontal is applied to the box. What is the minimum coefficient of static friction between the box and the surface required for the box to remain stationary?

A) 0.441
B) 0.654
C) 0.375
D) 0.866
E) 0.406

Question 80

A 50.0-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 20.7° below the horizontal is applied to the box. The coefficient of kinetic friction between the box and the surface is 0.300. What is the acceleration of the box?

A) 1.21 m/s²
B) 1.77 m/s²
C) 2.84 m/s²
D) 3.54 m/s²
E) 5.14 m/s²