Question 1

If a satellite moves above the Earth's atmosphere in a circular orbit with constant speed, then:

Accepted Answer

A)  its acceleration and velocity are in the same direction 
B)  the net force on it is zero 
C)  its velocity is constant 
D)  it will fall back to Earth when its fuel is used up 
E)  its acceleration is toward the Earth 
A)  its acceleration and velocity are in the same direction 
B)  the net force on it is zero 
C)  its velocity is constant 
D)  it will fall back to Earth when its fuel is used up 
E)  its acceleration is toward the Earth

Question 2

The coefficient of kinetic friction:

Accepted Answer

A)  is in the direction of the frictional force 
B)  is in the direction of the normal force 
C)  is the ratio of force to area 
D)  can have units of newtons 
E)  none of the above 
A)  is in the direction of the frictional force 
B)  is in the direction of the normal force 
C)  is the ratio of force to area 
D)  can have units of newtons 
E)  none of the above

Question 3

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 4

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)  zero 
B)  11800 N 
C)  1800 N 
D)  9800 N 
E)  none of these 
A)  zero 
B)  11800 N 
C)  1800 N 
D)  9800 N 
E)  none of these

Question 5

A crate is sliding down an incline that is   above the horizontal. If the coefficient of kinetic friction is 0.40, the acceleration of the crate is:

Accepted Answer

A)  0 
B)  2.4 m/s2 
C)  5.8 m/s2 
D)  8.8 m/s2 
E)  10.3 m/s2 
A)  0 
B)  2.4 m/s2 
C)  5.8 m/s2 
D)  8.8 m/s2 
E)  10.3 m/s2

Question 6

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 verticle is:

Accepted Answer

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

Question 7

A 5.0-kg crate is on an incline that makes an angle of  with the horizontal. If the coefficient of static friction is 0.50, the minimum force that can be applied parallel to the plane to hold the crate at rest is:

Accepted Answer

A)  0 
B)  3.3 N 
C)  30 N 
D)  46 N 
E)  55 N 
A)  0 
B)  3.3 N 
C)  30 N 
D)  46 N 
E)  55 N

Question 8

A 40-N crate rests on a rough horizontal floor. A 12-N horizonatl force is then applied to it. If the coefficients of friction are  $\mu$ s = 0.5 and  $\mu$ k = 0.4, the magnitude of the frictional force on the crate is:

Accepted Answer

A)  8 N 
B)  12 N 
C)  16 N 
D)  20 N 
E)  40 Nb 
A)  8 N 
B)  12 N 
C)  16 N 
D)  20 N 
E)  40 Nb

Question 9

A 400-N block is dragged along a horizonatl 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 Nb 
A)  100 N 
B)  150 N 
C)  200 N 
D)  290 N 
E)  400 Nb

Question 10

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  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 11

A giant wheel, having a diameter of 40 m, is fitted with a cage and platform on which a man of mass m stands. The wheel is rotated in a vertical plane at such a speed that the force exerted by the man on the platform is equal to his weight when the cage is at X, as shown. The net force on the man at point X is:

Accepted Answer

A)  zero 
B)  mg, down 
C)  mg, up 
D)  2 mg, down 
E)  2 mg, up 
A)  zero 
B)  mg, down 
C)  mg, up 
D)  2 mg, down 
E)  2 mg, up

Exam 6: Force and Motion II

If a satellite moves above the Earth's atmosphere in a circular orbit with constant speed, then:

The coefficient of kinetic friction:

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 crate is sliding down an incline that is 35 above the horizontal. If the coefficient of kinetic friction is 0.40, the acceleration of the crate 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 verticle is:

A 5.0-kg crate is on an incline that makes an angle of 30with the horizontal. If the coefficient of static friction is 0.50, the minimum force that can be applied parallel to the plane to hold the crate at rest is:

A 40-N crate rests on a rough horizontal floor. A 12-N horizonatl force is then applied to it. 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 crate is:

A 400-N block is dragged along a horizonatl 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 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 25with the horizontal, the force of friction is:

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A 40-N crate rests on a rough horizontal floor. A 12-N horizonatl force is then applied to it. If the coefficients of friction are $\mu$ _s = 0.5 and $\mu$ _k = 0.4, the magnitude of the frictional force on the crate is:

A 400-N block is dragged along a horizonatl 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: