Question 1

A baseball has a terminal speed of 42 m/s in air (ρ = 1.2 kg/m3). What would be its terminal speed in water (ρ = 1.0 x 103 kg/m3)?

Accepted Answer

A)  0.05 m/s 
B)  1.5 m/s 
C)  18 m/s 
D)  42 m/s 
E)  1200 m/s 
A)  0.05 m/s 
B)  1.5 m/s 
C)  18 m/s 
D)  42 m/s 
E)  1200 m/s

Question 2

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 3

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 4

A 24-N horizontal force is applied to a 40-N block initially at rest on a rough horizontal surface. If the coefficients of friction are $\mu$s = 0.5 and $\mu$k = 0.4, the magnitude of the frictional force on the block is:

Accepted Answer

A)  12 N 
B)  16 N 
C)  20 N 
D)  24 N 
E)  40 N 
A)  12 N 
B)  16 N 
C)  20 N 
D)  24 N 
E)  40 N

Question 5

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 6

The driver of a 1000-kg car tries to turn through a circle of radius 100 m on an unbanked curve at a speed of 10 m/s. The actual frictional force between the tires and a slippery road has a magnitude of 900 N. The car:

Accepted Answer

A)  slides into the inside of the curve 
B)  makes the turn 
C)  slows down due to the frictional force 
D)  will make the turn only if it goes faster 
E)  slides off to the outside of the curve 
A)  slides into the inside of the curve 
B)  makes the turn 
C)  slows down due to the frictional force 
D)  will make the turn only if it goes faster 
E)  slides off to the outside of the curve

Question 7

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, of block B, attached to the dangling end, for which A begins to slide down the incline, 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

Question 8

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 9

A cube has a drag coefficient of 0.8. What would be the terminal velocity of a sugar cube 1 cm on a side in air (ρ = 1.2 kg/m3)? Take the density of sugar to be 1.6 x 103 kg/m3.

Accepted Answer

A)  1.4 m/s 
B)  5 m/s 
C)  18 m/s 
D)  60 m/s 
E)  320 m/s 
A)  1.4 m/s 
B)  5 m/s 
C)  18 m/s 
D)  60 m/s 
E)  320 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 ball of mass m is thrown downward from the edge of a cliff with an initial speed that is three times the terminal speed. Initially the drag force on it is

Accepted Answer

A)  upward and greater than mg 
B)  upward and less than mg 
C)  downward and greater than mg 
D)  downward and less than mg 
E)  downward and equal to mg 
A)  upward and greater than mg 
B)  upward and less than mg 
C)  downward and greater than mg 
D)  downward and less than mg 
E)  downward and equal to mg

Question 12

An object moves in a circle. If the mass is tripled, the speed halved and the radius unchanged then the magnitude of the centripetal force must be multiplied by a factor of:

Accepted Answer

A)  3/2 
B)  3/4 
C)  9/4 
D)  6 
E)  12 
A)  3/2 
B)  3/4 
C)  9/4 
D)  6 
E)  12

Question 13

Circular freeway entrance and exit ramps are commonly banked to handle a car moving at 13 m/s. To design a similar ramp for 26 m/s one should:

Accepted Answer

A)  increase the radius by a factor of 2 
B)  decrease the radius by a factor of 2 
C)  increase the radius by a factor of 4 
D)  decrease the radius by a factor of 4 
E)  increase the radius by a factor of 
A)  increase the radius by a factor of 2 
B)  decrease the radius by a factor of 2 
C)  increase the radius by a factor of 4 
D)  decrease the radius by a factor of 4 
E)  increase the radius by a factor of

Question 14

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 baseball has a terminal speed of 42 m/s in air (ρ = 1.2 kg/m3). What would be its terminal speed in water (ρ = 1.0 x 103 kg/m3)?

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

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 24-N horizontal force is applied to a 40-N block initially at rest on a rough horizontal surface. If the coefficients of friction are μ\muμ s = 0.5 and μ\muμ k = 0.4, the magnitude of the frictional force on the block 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 driver of a 1000-kg car tries to turn through a circle of radius 100 m on an unbanked curve at a speed of 10 m/s. The actual frictional force between the tires and a slippery road has a magnitude of 900 N. The car:

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?

A cube has a drag coefficient of 0.8. What would be the terminal velocity of a sugar cube 1 cm on a side in air (ρ = 1.2 kg/m3)? Take the density of sugar to be 1.6 x 103 kg/m3.

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 ball of mass m is thrown downward from the edge of a cliff with an initial speed that is three times the terminal speed. Initially the drag force on it is

An object moves in a circle. If the mass is tripled, the speed halved and the radius unchanged then the magnitude of the centripetal force must be multiplied by a factor of:

Circular freeway entrance and exit ramps are commonly banked to handle a car moving at 13 m/s. To design a similar ramp for 26 m/s one should:

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 baseball has a terminal speed of 42 m/s in air (ρ = 1.2 kg/m³). What would be its terminal speed in water (ρ = 1.0 x 10³ kg/m³)?

A 24-N horizontal force is applied to a 40-N block initially at rest on a rough horizontal surface. If the coefficients of friction are $\mu$ _s = 0.5 and $\mu$ _k = 0.4, the magnitude of the frictional force on the 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 the coefficients of friction are $\mu$ _s = 0.60 and $\mu$ _k = 0.50 which of the following is true?

A cube has a drag coefficient of 0.8. What would be the terminal velocity of a sugar cube 1 cm on a side in air (ρ = 1.2 kg/m³)? Take the density of sugar to be 1.6 x 10³ kg/m³.

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?