Question 1

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If $\mu$s = 0.60 and $\mu$k = 0.50, the acceleration of the block is:

Accepted Answer

A) 0 m/s2 
B) 3.8 m/s2 
C) 4.8 m/s2 
D) 8.0 m/s2 
E) 9.8 m/s2 
A) 0 m/s2 
B) 3.8 m/s2 
C) 4.8 m/s2 
D) 8.0 m/s2 
E) 9.8 m/s2

Question 2

In uniform circular motion,

Accepted Answer

A) the acceleration is always constant in magnitude and direction. 
B) the velocity is always constant in magnitude and direction. 
C) both the acceleration and the velocity are continually changing direction. 
D) the velocity is always changing direction but the acceleration is always in the same direction. 
E) the net force is always constant in magnitude and direction. 
A) the acceleration is always constant in magnitude and direction. 
B) the velocity is always constant in magnitude and direction. 
C) both the acceleration and the velocity are continually changing direction. 
D) the velocity is always changing direction but the acceleration is always in the same direction. 
E) the net force is always constant in magnitude and direction.

Question 3

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

Question 4

A 0.2-kg stone is attached to a string and swung in a circle of radius 0.6 m on a horizontal and frictionless surface.If the stone makes 150 revolutions per minute, the tension force of the string on the stone is:

Accepted Answer

A) 0.03 N 
B) 0.2 N 
C) 0.75 N 
D) 1.96 N 
E) 30 N 
A) 0.03 N 
B) 0.2 N 
C) 0.75 N 
D) 1.96 N 
E) 30 N

Question 5

The system shown remains at rest.The force of friction on the block on the slope is:

Accepted Answer

A) 4 N 
B) 8 N 
C) 12 N 
D) 16 N 
E) 20 N 
A) 4 N 
B) 8 N 
C) 12 N 
D) 16 N 
E) 20 N

Question 6

A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force as shown.In the diagram f is the magnitude of the force of friction, N is the magnitude of the normal force, and Fg is the magnitude of the force of gravity.Which of the following must be true?

Accepted Answer

A) P = f and N = Fg  
B) P = f and N > Fg  
C) P > f and N g 
D) P > f and N = Fg 
E) none of these 
A) P = f and N = Fg  
B) P = f and N > Fg  
C) P > f and N g 
D) P > f and N = Fg 
E) none of these

Question 7

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

Question 8

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 9

A car is traveling at 15 m/s on a horizontal road.The brakes are applied and the car skids to a stop in 4.0 s.The coefficient of kinetic friction between the tires and road is:

Accepted Answer

A) 0.38 
B) 0.69 
C) 0.76 
D) 0.92 
E) 3.75 
A) 0.38 
B) 0.69 
C) 0.76 
D) 0.92 
E) 3.75

Question 10

A car rounds a 75-m radius curve at a constant speed of 18 m/s.A ball is suspended by a string from the ceiling the car and moves with the car.The angle between the string and the vertical is:

Accepted Answer

A) 0° 
B) 1.4° 
C) 24° 
D) 90° 
E) cannot be found without knowing the mass of the ball 
A) 0° 
B) 1.4° 
C) 24° 
D) 90° 
E) cannot be found without knowing the mass of the ball

Question 11

A crate resting on a rough horizontal floor is to be moved horizontally.The coefficient of static friction is 0.40.To start the crate moving with the weakest possible applied force, in what direction should the force be applied?

Accepted Answer

A) Horizontal 
B) 24$\degree$ below the horizontal 
C) 22$\degree$above the horizontal 
D) 24$\degree$above the horizontal 
E) 66$\degree$ below the horizontal 
A) Horizontal 
B) 24$\degree$ below the horizontal 
C) 22$\degree$above the horizontal 
D) 24$\degree$above the horizontal 
E) 66$\degree$ below the horizontal

Question 12

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

Question 13

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

Question 14

An object moves around a circle.If the radius is doubled keeping the speed the same then the magnitude of the centripetal force must be:

Accepted Answer

A) twice as great 
B) half as great 
C) four times as great 
D) one-fourth as great 
E) the same 
A) twice as great 
B) half as great 
C) four times as great 
D) one-fourth as great 
E) the same

Question 15

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If the coefficients of friction are $\mu$s = 0.60 and $\mu$k = 0.50 which of the following is true?

Accepted Answer

A) The frictional force is 4.9 N 
B) The frictional force is 7.2 N 
C) The normal force is 4.9 N 
D) The block will start moving and accelerate 
E) If started moving downward, the block will accelerate 
A) The frictional force is 4.9 N 
B) The frictional force is 7.2 N 
C) The normal force is 4.9 N 
D) The block will start moving and accelerate 
E) If started moving downward, the block will accelerate

Question 16

An object of mass m and another object of mass 2m are each forced to move along a circle of radius 1.0 m at a constant speed of 1.0 m/s.The magnitudes of their accelerations are:

Accepted Answer

A) equal 
B) in the ratio of : 1 
C) in the ratio of 2 : 1 
D) in the ratio of 4 : 1 
E) zero 
A) equal 
B) in the ratio of : 1 
C) in the ratio of 2 : 1 
D) in the ratio of 4 : 1 
E) zero

Question 17

A 1000-kg airplane moves in straight flight at constant speed.The force of air friction is 1800 N.The net force on the plane is:

Accepted Answer

A) 0 N 
B) 11600 N 
C) 1800 N 
D) 9800 N 
E) none of these 
A) 0 N 
B) 11600 N 
C) 1800 N 
D) 9800 N 
E) none of these

Question 18

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 19

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 20

Block A, with a mass of 10 kg, rests on a 35$\degree$incline.The coefficient of static friction is 0.40.An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top.The largest mass mB, attached to the dangling end, for which A remains at rest is:

Accepted Answer

A) 2.5 kg 
B) 3.5 kg 
C) 5.9 kg 
D) 9.0 kg 
E) 10.5 kg 
A) 2.5 kg 
B) 3.5 kg 
C) 5.9 kg 
D) 9.0 kg 
E) 10.5 kg

Exam 6: Force and Motion II

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If μ\muμ s = 0.60 and μ\muμ k = 0.50, the acceleration of the block is:

In uniform circular motion,

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:

A 0.2-kg stone is attached to a string and swung in a circle of radius 0.6 m on a horizontal and frictionless surface.If the stone makes 150 revolutions per minute, the tension force of the string on the stone is:

The system shown remains at rest.The force of friction on the block on the slope is:

A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force as shown.In the diagram f is the magnitude of the force of friction, N is the magnitude of the normal force, and Fg is the magnitude of the force of gravity.Which of the following must be true?

A car is traveling at 15 m/s on a horizontal road.The brakes are applied and the car skids to a stop in 4.0 s.The coefficient of kinetic friction between the tires and road is:

A car rounds a 75-m radius curve at a constant speed of 18 m/s.A ball is suspended by a string from the ceiling the car and moves with the car.The angle between the string and the vertical is:

A crate resting on a rough horizontal floor is to be moved horizontally.The coefficient of static friction is 0.40.To start the crate moving with the weakest possible applied force, in what direction should the force be applied?

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:

An object moving in a circle at constant speed:

An object moves around a circle.If the radius is doubled keeping the speed the same then the magnitude of the centripetal force must be:

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If the coefficients of friction are μ\muμ s = 0.60 and μ\muμ k = 0.50 which of the following is true?

An object of mass m and another object of mass 2m are each forced to move along a circle of radius 1.0 m at a constant speed of 1.0 m/s.The magnitudes of their accelerations are:

A 1000-kg airplane moves in straight flight at constant speed.The force of air friction is 1800 N.The net force on the plane 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:

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:

Block A, with a mass of 10 kg, rests on a 35 °\degree° incline.The coefficient of static friction is 0.40.An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top.The largest mass mB, attached to the dangling end, for which A remains at rest is:

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A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If $\mu$ _s = 0.60 and $\mu$ _k = 0.50, the acceleration of the block is:

A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force as shown.In the diagram f is the magnitude of the force of friction, N is the magnitude of the normal force, and F_g is the magnitude of the force of gravity.Which of the following must be true?

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If the coefficients of friction are $\mu$ _s = 0.60 and $\mu$ _k = 0.50 which of the following is true?

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: