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 $\theta$

Question 2

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If    = 0.60 and   = 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 3

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 4

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 5

Block A, with a mass of 10 kg, rests on a 30°incline.The coefficient of kinetic friction is 0.20.The attached string is parallel to the incline and passes over a massless, frictionless pulley at the top.Block B, with a mass of 3.0 kg, is attached to the dangling end of the string.The acceleration of B is:

Accepted Answer

A) 0.20 m/s2, up 
B) 0.20 m/s2, down 
C) 2.8 m/s2, up 
D) 2.8 m/s2, down 
E) 0 m/s2 
A) 0.20 m/s2, up 
B) 0.20 m/s2, down 
C) 2.8 m/s2, up 
D) 2.8 m/s2, down 
E) 0 m/s2

Question 6

A brick slides on a horizontal surface.Which of the following will increase the frictional force on it?

Accepted Answer

A) Putting a second brick on top 
B) Decreasing the surface area of contact 
C) Increasing the surface area of contact 
D) Decreasing the mass of the brick 
E) None of the above 
A) Putting a second brick on top 
B) Decreasing the surface area of contact 
C) Increasing the surface area of contact 
D) Decreasing the mass of the brick 
E) None of the above

Question 7

In uniform circular motion,

Accepted Answer

A) the acceleration always points away from the center of the circle. 
B) the velocity always points towards the center of the circle. 
C) the acceleration and the velocity are always parallel. 
D) the acceleration and the velocity are always perpendicular. 
E) there is no fixed relationship between the direction of the acceleration and the direction of the velocity. 
A) the acceleration always points away from the center of the circle. 
B) the velocity always points towards the center of the circle. 
C) the acceleration and the velocity are always parallel. 
D) the acceleration and the velocity are always perpendicular. 
E) there is no fixed relationship between the direction of the acceleration and the direction of the velocity.

Question 8

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 9

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

Accepted Answer

A) T cos $\theta$ 
B) T sin$\theta$ 
C) 0 
D) mg 
E) mg cos$\theta$ 
A) T cos $\theta$ 
B) T sin$\theta$ 
C) 0 
D) mg 
E) mg cos$\theta$

Question 10

A box with a weight of 50 N rests on a horizontal surface.A person pulls horizontally on it with a force of 15 N and it does not move.To start it moving, a second person pulls vertically upward on the box.If the coefficient of static friction is 0.4, what is the smallest vertical force for which the box moves?

Accepted Answer

A) 5 N 
B) 12 N 
C) 20 N 
D) 25 N 
E) 35 N 
A) 5 N 
B) 12 N 
C) 20 N 
D) 25 N 
E) 35 N

Question 11

A horizontal shove of at least 200-N is required to start moving an 800-N crate initially at rest on a horizontal floor.The coefficient of static friction is:

Accepted Answer

A) 0.125 
B) 0.25 
C) 0.50 
D) 4.00 
E) none of these 
A) 0.125 
B) 0.25 
C) 0.50 
D) 4.00 
E) none of these

Question 12

A 5.0-kg crate is on an incline that makes an angle 30° with the horizontal.If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

Accepted Answer

A) 0 N 
B) 3.3 N 
C) 21 N 
D) 46 N 
E) 55 N 
A) 0 N 
B) 3.3 N 
C) 21 N 
D) 46 N 
E) 55 N

Question 13

Block A, with a mass of 10 kg, rests on a 30°incline.The coefficient of kinetic friction is 0.20.The attached string is parallel to the incline and passes over a massless, frictionless pulley at the top.Block B, with a mass of 8.0 kg, is attached to the dangling end of the string.The acceleration of B is:

Accepted Answer

A) 0.69 m/s2, up 
B) 0.69 m/s2, down 
C) 2.6 m/s2, up 
D) 2.6 m/s2, down 
E) 0 m/s2 
A) 0.69 m/s2, up 
B) 0.69 m/s2, down 
C) 2.6 m/s2, up 
D) 2.6 m/s2, down 
E) 0 m/s2

Question 14

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   = 0.5 and   = 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 15

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°above the horizontal 
C) 30° above the horizontal 
D) 27° above the horizontal 
E) 30° below the horizontal 
A) Horizontal 
B) 60°above the horizontal 
C) 30° above the horizontal 
D) 27° above the horizontal 
E) 30° below the horizontal

Question 16

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 17

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 
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 18

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 19

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° below the horizontal 
C) 22° above the horizontal 
D) 24° above the horizontal 
E) 66° below the horizontal 
A) Horizontal 
B) 24° below the horizontal 
C) 22° above the horizontal 
D) 24° above the horizontal 
E) 66° below the horizontal

Question 20

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

Exam 6: Force and Motion

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 horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If = 0.60 and = 0.50, the acceleration of the block 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 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 brick slides on a horizontal surface.Which of the following will increase the frictional force on it?

In uniform circular motion,

The coefficient of kinetic friction:

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

A horizontal shove of at least 200-N is required to start moving an 800-N crate initially at rest on a horizontal floor.The coefficient of static friction is:

A 5.0-kg crate is on an incline that makes an angle 30° with the horizontal.If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

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 = 0.5 and = 0.4, the magnitude of the frictional force on the block 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 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?

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 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 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

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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 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?