Question 1

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

Question 2

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

Question 3

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

Question 4

A block of mass m is pulled at constant velocity along a rough horizonatl floor by and applied force  as shown. The magnitude of frictional force is:

Accepted Answer

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

Question 5

A ball is thrown upward into the air with a speed that is greater than terminal speed. It lands at the place where it was thrown. During its flight the force of air resistance is the greatest:

Accepted Answer

A)  just after it is thrown 
B)  halfway up 
C)  at the top of its trajectory 
D)  halfway down 
E)  just before it lands

Question 6

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)  above the horizontal 
C)   above the horizontal 
D)   above the horizontal 
E)   below the horizontal

Question 7

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*10-2 N. 
D)  2.4-2 *10-2 N 
E)  3.13 N

Question 8

A crate rests on a horizontal surface and a woman pulls on it with a 10-N force. No matter what the orientation of the force, the crate does not move. Rank the situations shown below according to the magnitude of the frictional force of the surface on the crate, least to greatest.

Accepted Answer

A)  1, 2, 3 
B)  2, 1, 3 
C)  2, 3, 1 
D)  1, 3, 2 
E)  3, 2, 1

Question 9

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° 
C)  42° 
D)  65° 
E)  90°

Question 10

Block A, with a mass of 10 kg, rests on a 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

Question 11

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)  1.11

Question 12

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)   below the horizontal 
C)   above the horizontal 
D)   above the horizontal 
E)  below the horizontal

Question 13

A horizontal force of 12 N pushes a 0.5-kg bookk against a vertical wall. The book is initially at rest. If the coefficients of friction are $\mu$s = 0.6 and $\mu$k = 0.8 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 decelerate

Question 14

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

Question 15

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

Question 16

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 = 0.6 and $\mu$k = 0.80, the frictional force is:

Accepted Answer

A)  0 
B)  4.9 N 
C)  3.0 N 
D)  5.0 N 
E)  4.0 N

Question 17

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

Question 18

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

Question 19

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$\theta$

Question 20

Why do raindrops fall with constant speed during the later stages of their descent?

Accepted Answer

A)  The gravitational force is the same for all drops 
B)  Air resistance just balances the force of gravity 
C)  The drops all fall from the same height 
D)  The force of gravity is negligible for objects as small as raindrops 
E)  Gravity cannot increase the speed of a falling object to more than 32 ft/s

Exam 6: Force and Motion II

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 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:

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

A ball is thrown upward into the air with a speed that is greater than terminal speed. It lands at the place where it was thrown. During its flight the force of air resistance is the greatest:

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 crate rests on a horizontal surface and a woman pulls on it with a 10-N force. No matter what the orientation of the force, the crate does not move. Rank the situations shown below according to the magnitude of the frictional force of the surface on the crate, least to greatest.

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?

Block A, with a mass of 10 kg, rests on a 35incline. 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 m_B, attached to the dangling end, for which A remains at rest is:

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 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 horizontal force of 12 N pushes a 0.5-kg bookk against a vertical wall. The book is initially at rest. If the coefficients of friction are $\mu$ _s = 0.6 and $\mu$ _k = 0.8 which of the following is true?

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 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:

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 = 0.6 and $\mu$ _k = 0.80, the frictional force is:

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:

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

Why do raindrops fall with constant speed during the later stages of their descent?

Exam 6: Force and Motion II

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 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:

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

A block of mass m is pulled at constant velocity along a rough horizonatl floor by and applied force as shown. The magnitude of frictional force is:

A ball is thrown upward into the air with a speed that is greater than terminal speed. It lands at the place where it was thrown. During its flight the force of air resistance is the greatest:

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 crate rests on a horizontal surface and a woman pulls on it with a 10-N force. No matter what the orientation of the force, the crate does not move. Rank the situations shown below according to the magnitude of the frictional force of the surface on the crate, least to greatest.

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?

Block A, with a mass of 10 kg, rests on a 35incline. 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:

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 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 horizontal force of 12 N pushes a 0.5-kg bookk against a vertical wall. The book is initially at rest. If the coefficients of friction are μ\muμ s = 0.6 and μ\muμ k = 0.8 which of the following is true?

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 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:

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 = 0.6 and μ\muμ k = 0.80, the frictional force is:

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:

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

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:

Why do raindrops fall with constant speed during the later stages of their descent?

Block A, with a mass of 10 kg, rests on a 35incline. 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 m_B, attached to the dangling end, for which A remains at rest is:

A horizontal force of 12 N pushes a 0.5-kg bookk against a vertical wall. The book is initially at rest. If the coefficients of friction are $\mu$ _s = 0.6 and $\mu$ _k = 0.8 which of the following is true?

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:

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 = 0.6 and $\mu$ _k = 0.80, the frictional force is: