Question 1

An object moving in a circle at constant speed:

Accepted Answer

A)  must have only one force acting on it 
B)  is not accelerating 
C)  is held to its path by centrifugal force 
D)  has an acceleration of constant magnitude 
E)  has an acceleration that is tangent to the circle 
A)  must have only one force acting on it 
B)  is not accelerating 
C)  is held to its path by centrifugal force 
D)  has an acceleration of constant magnitude 
E)  has an acceleration that is tangent to the circle D

Question 2

A coin is placed on a horizontal phonograph turntable. Let N be the normal force exerted by the turntable on the coin, f be the frictional force exerted by the turntable on the coin, and fs, max be the maximum force of the static friction. The speed of the turntable is increased in small steps. If the coin does not slide, then

Accepted Answer

A)  N increases, f increases, and fs, max stays the same 
B)  N increases, f increases, and fs, max increases 
C)  f increases and both N and fs, max stay the same 
D)  N, f, and fs, max all stay the same 
E)  N, f, and fs, max all increase 
A)  N increases, f increases, and fs, max stays the same 
B)  N increases, f increases, and fs, max increases 
C)  f increases and both N and fs, max stay the same 
D)  N, f, and fs, max all stay the same 
E)  N, f, and fs, max all increase C

Question 3

An 800-N passenger in a car presses against the car door with a 200 N force when the car makes a left turn at 13 m/s. The (faulty) door will pop open under a force of 800 N. Of the following, the least speed for which the man is thrown out of the car is:

Accepted Answer

A)  14 m/s 
B)  19 m/s 
C)  20 m/s 
D)  26 m/s 
E)  52 m/s 
A)  14 m/s 
B)  19 m/s 
C)  20 m/s 
D)  26 m/s 
E)  52 m/s D

Question 4

One end of a 1.0-m string is fixed; the other end is attached to a 2.0-kg stone. The stone swings in a vertical circle, passing the top point at 4.0 m/s. The tension force of the string at this point is about:

Accepted Answer

A)  0 N 
B)  12 N 
C)  20 N 
D)  32 N 
E)  52 N 
A)  0 N 
B)  12 N 
C)  20 N 
D)  32 N 
E)  52 N

Question 5

A bureau rests on a rough horizontal surface ($\mu$s = 0.50, $\mu$k = 0.40). A constant horizontal force, just sufficient to start the bureau in motion, is then applied. The acceleration of the bureau is:

Accepted Answer

A)  0 m/s2 
B)  0.98 m/s2 
C)  3.9 m/s2 
D)  4.9 m/s2 
E)  8.8 m/s2 
A)  0 m/s2 
B)  0.98 m/s2 
C)  3.9 m/s2 
D)  4.9 m/s2 
E)  8.8 m/s2

Question 6

A 400-N block is dragged along a horizontal surface by an applied force as shown. The coefficient of kinetic friction is uk = 0.4 and the block moves at constant velocity. The magnitude of is:

Accepted Answer

A)  100 N 
B)  150 N 
C)  200 N 
D)  290 N 
E)  400 N 
A)  100 N 
B)  150 N 
C)  200 N 
D)  290 N 
E)  400 N

Question 7

A 50-N force is applied to a crate on a horizontal rough floor, causing it to move horizontally. If the coefficient of kinetic friction is 0.50, in what direction should the force be applied to obtain the greatest acceleration?

Accepted Answer

A)  Horizontal 
B)  60 $\degree$ above the horizontal 
C)  30 $\degree$above the horizontal 
D)  27 $\degree$ above the horizontal 
E)  30 $\degree$ below the horizontal 
A)  Horizontal 
B)  60 $\degree$ above the horizontal 
C)  30 $\degree$above the horizontal 
D)  27 $\degree$ above the horizontal 
E)  30 $\degree$ below the horizontal

Question 8

The magnitude of the force required to cause an 0.04-kg object to move at 0.6 m/s in a circle of radius 1.0 m is:

Accepted Answer

A)  2.4 * 10-2 N 
B)  1.4 * 10-2 N 
C)  1.4 $\pi$ * 10-2 N 
D)  2.4 $\pi$2 * 10-2 N 
E)  3.13 N 
A)  2.4 * 10-2 N 
B)  1.4 * 10-2 N 
C)  1.4 $\pi$ * 10-2 N 
D)  2.4 $\pi$2 * 10-2 N 
E)  3.13 N

Question 9

A box rests on a rough board 10 meters long. When one end of the board is slowly raised to a height of 6 meters above the other end, the box begins to slide. The coefficient of static friction is:

Accepted Answer

A)  0.8 
B)  0.25 
C)  0.4 
D)  0.6 
E)  0.75 
A)  0.8 
B)  0.25 
C)  0.4 
D)  0.6 
E)  0.75

Question 10

Which of the following five graphs is correct for a particle moving in a circle of radius r at a constant speed of 10 m/s?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
E)  V 
A)  I 
B)  II 
C)  III 
D)  IV 
E)  V

Question 11

Block A, with a mass of 50 kg, rests on a horizontal table top. The coefficient of static friction is 0.40. A horizontal string is attached to A and passes over a massless, frictionless pulley as shown. The smallest mass mB of block B, attached to the dangling end, that will start A moving when it is attached to the other end of the string is:

Accepted Answer

A)  20 kg 
B)  30 kg 
C)  40 kg 
D)  50 kg 
E)  70 kg 
A)  20 kg 
B)  30 kg 
C)  40 kg 
D)  50 kg 
E)  70 kg

Question 12

Block A, with mass mA, is initially at rest on a horizontal floor. Block B, with mass mB, is initially at rest on the horizontal top surface of A. The coefficient of static friction between the two blocks is $\mu$s. Block A is pulled with a horizontal force. It begins to slide out from under B if the force is greater than:

Accepted Answer

A)  mAg 
B)  mBg 
C)  $\mu$smAg 
D)  $\mu$smBg 
E)  $\mu$s ( mA + m
B) g 
A)  mAg 
B)  mBg 
C)  $\mu$smAg 
D)  $\mu$smBg 
E)  $\mu$s ( mA + m
B) g

Question 13

A 5.0-kg crate is resting on a horizontal plank. The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40. After one end of the plank is raised so the plank makes an angle of 25$\degree$ with the horizontal, the force of friction is:

Accepted Answer

A)  0 N 
B)  20 N 
C)  21 N 
D)  22 N 
E)  44 N 
A)  0 N 
B)  20 N 
C)  21 N 
D)  22 N 
E)  44 N

Question 14

Block A, with a mass of 10 kg, rests on a 30$\degree$incline. The coefficient of kinetic friction is 0.20. The attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. Block B, with a mass of 3.0 kg, is attached to the dangling end of the string. The acceleration of B is:

Accepted Answer

A)  0.20 m/s2, up 
B)  0.20 m/s2, down 
C)  2.8 m/s2, up 
D)  2.8 m/s2, down 
E)  0 m/s2 
A)  0.20 m/s2, up 
B)  0.20 m/s2, down 
C)  2.8 m/s2, up 
D)  2.8 m/s2, down 
E)  0 m/s2

Question 15

If a certain car, going with speed v1, rounds a level curve with a radius R1, it is just on the verge of skidding. If its speed is now doubled, the radius of the tightest curve on the same road that it can round without skidding is:

Accepted Answer

A)  2R1 
B)  4R1 
C)  R1/2 
D)  R1/4 
E)  R1 
A)  2R1 
B)  4R1 
C)  R1/2 
D)  R1/4 
E)  R1

Question 16

Uniform circular motion is the direct consequence of:

Accepted Answer

A)  Newton's third law 
B)  a force that is always tangent to the path 
C)  an acceleration tangent to the path 
D)  a force of constant magnitude that is always directed away from the same fixed point 
E)  a force of constant magnitude that is always directed toward the same fixed point 
A)  Newton's third law 
B)  a force that is always tangent to the path 
C)  an acceleration tangent to the path 
D)  a force of constant magnitude that is always directed away from the same fixed point 
E)  a force of constant magnitude that is always directed toward the same fixed point

Question 17

A block of mass m is pulled along a rough horizontal floor by an applied force as shown. The vertical component of the force exerted on the block by the floor is:

Accepted Answer

A)  mg 
B)  mg - T cos $\theta$ 
C)  mg + T cos $\theta$ 
D)  mg - T sin$\theta$ 
E)  mg + T sin $\theta$ 
A)  mg 
B)  mg - T cos $\theta$ 
C)  mg + T cos $\theta$ 
D)  mg - T sin$\theta$ 
E)  mg + T sin $\theta$

Question 18

A 5.0-kg crate is on an incline that makes an angle 30$\degree$ with the horizontal. If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

Accepted Answer

A)  0 N 
B)  3.3 N 
C)  21 N 
D)  46 N 
E)  55 N 
A)  0 N 
B)  3.3 N 
C)  21 N 
D)  46 N 
E)  55 N

Question 19

A block is placed on a rough wooden plane. It is found that when the plane is tilted 30$\degree$to the horizontal, the block will slide down at constant speed. The coefficient of kinetic friction of the block with the plane is:

Accepted Answer

A)  0.500 
B)  0.577 
C)  1.73 
D)  0.866 
E)  4.90 
A)  0.500 
B)  0.577 
C)  1.73 
D)  0.866 
E)  4.90

Question 20

A block is first placed on its long side and then on its short side on the same inclined plane. The block slides down the plane on its short side but remains at rest on its long side. A possible explanation is:

Accepted Answer

A)  the short side is smoother 
B)  the frictional force is less because the contact area is less 
C)  the center of gravity is higher in the second case 
D)  the normal force is less in the second case 
E)  the force of gravity is more nearly down the plane in the second case 
A)  the short side is smoother 
B)  the frictional force is less because the contact area is less 
C)  the center of gravity is higher in the second case 
D)  the normal force is less in the second case 
E)  the force of gravity is more nearly down the plane in the second case

Exam 6: Force and Motion II

An object moving in a circle at constant speed:

An 800-N passenger in a car presses against the car door with a 200 N force when the car makes a left turn at 13 m/s. The (faulty) door will pop open under a force of 800 N. Of the following, the least speed for which the man is thrown out of the car is:

One end of a 1.0-m string is fixed; the other end is attached to a 2.0-kg stone. The stone swings in a vertical circle, passing the top point at 4.0 m/s. The tension force of the string at this point is about:

A bureau rests on a rough horizontal surface ( μ\muμ s = 0.50, μ\muμ k = 0.40). A constant horizontal force, just sufficient to start the bureau in motion, is then applied. The acceleration of the bureau is:

A 400-N block is dragged along a horizontal surface by an applied force as shown. The coefficient of kinetic friction is uk = 0.4 and the block moves at constant velocity. The magnitude of is:

A 50-N force is applied to a crate on a horizontal rough floor, causing it to move horizontally. If the coefficient of kinetic friction is 0.50, in what direction should the force be applied to obtain the greatest acceleration?

The magnitude of the force required to cause an 0.04-kg object to move at 0.6 m/s in a circle of radius 1.0 m is:

A box rests on a rough board 10 meters long. When one end of the board is slowly raised to a height of 6 meters above the other end, the box begins to slide. The coefficient of static friction is:

Which of the following five graphs is correct for a particle moving in a circle of radius r at a constant speed of 10 m/s?

A 5.0-kg crate is resting on a horizontal plank. The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40. After one end of the plank is raised so the plank makes an angle of 25 °\degree° with the horizontal, the force of friction is:

If a certain car, going with speed v1, rounds a level curve with a radius R1, it is just on the verge of skidding. If its speed is now doubled, the radius of the tightest curve on the same road that it can round without skidding is:

Uniform circular motion is the direct consequence of:

A block of mass m is pulled along a rough horizontal floor by an applied force as shown. The vertical component of the force exerted on the block by the floor is:

A 5.0-kg crate is on an incline that makes an angle 30 °\degree° with the horizontal. If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

A block is placed on a rough wooden plane. It is found that when the plane is tilted 30 °\degree° to the horizontal, the block will slide down at constant speed. The coefficient of kinetic friction of the block with the plane is:

A block is first placed on its long side and then on its short side on the same inclined plane. The block slides down the plane on its short side but remains at rest on its long side. A possible explanation is:

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A bureau rests on a rough horizontal surface ( $\mu$ _s = 0.50, $\mu$ _k = 0.40). A constant horizontal force, just sufficient to start the bureau in motion, is then applied. The acceleration of the bureau is:

A 400-N block is dragged along a horizontal surface by an applied force as shown. The coefficient of kinetic friction is u_k = 0.4 and the block moves at constant velocity. The magnitude of is:

A 5.0-kg crate is resting on a horizontal plank. The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40. After one end of the plank is raised so the plank makes an angle of 25 $\degree$ with the horizontal, the force of friction is:

If a certain car, going with speed v₁, rounds a level curve with a radius R₁, it is just on the verge of skidding. If its speed is now doubled, the radius of the tightest curve on the same road that it can round without skidding is:

A 5.0-kg crate is on an incline that makes an angle 30 $\degree$ with the horizontal. If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

A block is placed on a rough wooden plane. It is found that when the plane is tilted 30 $\degree$ to the horizontal, the block will slide down at constant speed. The coefficient of kinetic friction of the block with the plane is: