Question 1

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 $\theta$ D

Question 2

A block is suspended by a rope from the ceiling of a car.. When the car rounds a 45-m radius horizontal curve at 22 m/s (about 50 mph), what angle does the rod make with the vertical?

Accepted Answer

A)  0 
B)  25$\degree$ 
C)  42$\degree$ 
D)  65$\degree$ 
E)  90$\degree$ 
A)  0 
B)  25$\degree$ 
C)  42$\degree$ 
D)  65$\degree$ 
E)  90$\degree$ C

Question 3

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 A

Question 4

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 5

A professor holds an eraser against a vertical chalkboard by pushing horizontally on it. He pushes with a force that is much greater than is required to hold the eraser. The force of friction exerted by the board on the eraser increases if he:

Accepted Answer

A)  pushes with slightly greater force 
B)  pushes with slightly less force 
C)  stops pushing 
D)  pushes so his force is slightly downward but has the same magnitude 
E)  pushes so his force is slightly upward but has the same magnitude 
A)  pushes with slightly greater force 
B)  pushes with slightly less force 
C)  stops pushing 
D)  pushes so his force is slightly downward but has the same magnitude 
E)  pushes so his force is slightly upward but has the same magnitude

Question 6

A forward horizontal force of 12 N is used to pull a 240-N crate at constant velocity across a horizontal floor. The coefficient of friction is:

Accepted Answer

A)  0.5 
B)  0.05 
C)  2 
D)  0.2 
E)  20 
A)  0.5 
B)  0.05 
C)  2 
D)  0.2 
E)  20

Question 7

A person riding a Ferris wheel is strapped into her seat by a seat belt. The wheel is spun so that the centripetal acceleration is g. Select the correct combination of forces that act on her when she is at the top. In the table, Fg = force of gravity, down; Fb = seat belt force, down; and Fs = seat force, up.

Accepted Answer

A)  Fg = 0, Fb = mg, Fs = 0 
B)  Fg = mg, Fb = 0, Fs = 0 
C)  Fg = 0, Fb = 0, Fs = mg 
D)  Fg = mg, Fb = mg, Fs = 0 
E)  Fg = mg, Fb = 0, Fs = mg 
A)  Fg = 0, Fb = mg, Fs = 0 
B)  Fg = mg, Fb = 0, Fs = 0 
C)  Fg = 0, Fb = 0, Fs = mg 
D)  Fg = mg, Fb = mg, Fs = 0 
E)  Fg = mg, Fb = 0, Fs = mg

Question 8

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 
B)  0.98 m/s 2 
C)  3.3 m/s 2 
D)  4.5 m/s 2 
E)  8.9 m/s 2 
A)  0 
B)  0.98 m/s 2 
C)  3.3 m/s 2 
D)  4.5 m/s 2 
E)  8.9 m/s 2

Question 9

The iron ball shown is being swung in a vertical circle at the end of a 0.7-m string. How slowly, in ft/s, can the ball go through its top position without having the string go slack?

Accepted Answer

A)  1.3 m/s 
B)  2.6 m/s 
C)  3.9 m/s 
D)  6.9 m/s 
E)  9.8 m/s 
A)  1.3 m/s 
B)  2.6 m/s 
C)  3.9 m/s 
D)  6.9 m/s 
E)  9.8 m/s

Question 10

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 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

A giant wheel, 40 m in diameter, is fitted with a cage and platform on which a man can stand. The wheel rotates at such a speed that when the cage is at X (as shown) the force exerted by the man on the platform is equal to his weight. The speed of the man is:

Accepted Answer

A)  14 m/s 
B)  20 m/s 
C)  28 m/s 
D)  80 m/s 
E)  120 m/s 
A)  14 m/s 
B)  20 m/s 
C)  28 m/s 
D)  80 m/s 
E)  120 m/s

Question 13

The system shown remains at rest. The force of friction on the upper block 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 14

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall. The book is initially at rest. If $\mu$s = 0.6 and $\mu$k = 0.80, the acceleration of the book in m/s2 is:

Accepted Answer

A)  0 
B)  9.4 m/s2 
C)  9.8 m/s2 
D)  14.4 m/s2 
E)  19.2 m/s2 
A)  0 
B)  9.4 m/s2 
C)  9.8 m/s2 
D)  14.4 m/s2 
E)  19.2 m/s2

Question 15

When the brakes of an automobile are applied, the road exerts the greatest retarding force:

Accepted Answer

A)  while the wheels are sliding 
B)  just before the wheels start to slide 
C)  when the automobile is going fastest 
D)  when the acceleration is least 
E)  at the instant when the speed begins to change 
A)  while the wheels are sliding 
B)  just before the wheels start to slide 
C)  when the automobile is going fastest 
D)  when the acceleration is least 
E)  at the instant when the speed begins to change

Question 16

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

Accepted Answer

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

Question 17

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 30$\degree$ with the horizontal, the force of friction is:

Accepted Answer

A)  0 
B)  18 N 
C)  21 N 
D)  22 N 
E)  44 N 
A)  0 
B)  18 N 
C)  21 N 
D)  22 N 
E)  44 N

Question 18

The speed of a 4.0-N hockey puck, sliding across a level ice surface, decreases at the rate of 0.61 m/s2. The coefficient of kinetic friction between the puck and ice is:

Accepted Answer

A)  0.062 
B)  0.41 
C)  0.62 
D)  1.2 
E)  9.8 
A)  0.062 
B)  0.41 
C)  0.62 
D)  1.2 
E)  9.8

Question 19

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 20

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 = 0.80, the acceleration of the block in m/s2 is:

Accepted Answer

A)  0 
B)  1.8 
C)  6.0 
D)  8.0 
E)  9.8 
A)  0 
B)  1.8 
C)  6.0 
D)  8.0 
E)  9.8

Exam 6: Force and Motion II

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 block is suspended by a rope from the ceiling of a car.. When the car rounds a 45-m radius horizontal curve at 22 m/s (about 50 mph), what angle does the rod make with the vertical?

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 professor holds an eraser against a vertical chalkboard by pushing horizontally on it. He pushes with a force that is much greater than is required to hold the eraser. The force of friction exerted by the board on the eraser increases if he:

A forward horizontal force of 12 N is used to pull a 240-N crate at constant velocity across a horizontal floor. The coefficient of 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:

The iron ball shown is being swung in a vertical circle at the end of a 0.7-m string. How slowly, in ft/s, can the ball go through its top position without having the string go slack?

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 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?

A giant wheel, 40 m in diameter, is fitted with a cage and platform on which a man can stand. The wheel rotates at such a speed that when the cage is at X (as shown) the force exerted by the man on the platform is equal to his weight. The speed of the man is:

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

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall. The book is initially at rest. If μ\muμ s = 0.6 and μ\muμ k = 0.80, the acceleration of the book in m/s2 is:

When the brakes of an automobile are applied, the road exerts the greatest retarding force:

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

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 30 °\degree° with the horizontal, the force of friction is:

The speed of a 4.0-N hockey puck, sliding across a level ice surface, decreases at the rate of 0.61 m/s2. The coefficient of kinetic friction between the puck and ice 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?

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 = 0.80, the acceleration of the block in m/s2 is:

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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_gis the magnitude of the force of gravity. Which of the following must be 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:

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 $\mu$ _s = 0.6 and $\mu$ _k = 0.80, the acceleration of the book in m/s²is:

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 30 $\degree$ with the horizontal, the force of friction is:

The speed of a 4.0-N hockey puck, sliding across a level ice surface, decreases at the rate of 0.61 m/s². The coefficient of kinetic friction between the puck and ice is:

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 = 0.80, the acceleration of the block in m/s² is: