QUIZ FRICTION FORCE

A boy exerts a 36-N horizontal force as he pulls a 52-N sled across a cement sidewalk at constant speed. What is the coefficient of kinetic friction between the sidewalk and the metal sled runners? Ignore air resistance.

• 1.6

• 0.69

• 1.7

• 0.70

A horse pulls a cart along a flat road. Consider the following four forces that

arise in this situation.

(1) the force of the horse pulling on the cart

(2) the force of the cart pulling on the horse

(3) the force of the horse pushing on the road

(4) the force of the road pushing on the horse

Which two forces form an "action-reaction" pair that obeys Newton's third law?

• 1 and 4

• 3 and 4

• 2 and 3

• 2 and 4

A 7.0 kg box is at rest on the table. The static friction coefficient μ_s between the box and table is 0.40, and the kinetic friction coefficient μ_k is 0.10. Then, a 25 N horizontal force is applied to the box. What will happen to the box?

• The box will move opposite to the direction of the force.

• The box will stay at rest.

• The box will move relative to the direction of the force.

• The box will move with constant acceleration.

A book is resting on the surface of a table. Consider the following four forces

that arise in this situation:

(1) the force of the earth pulling on the book

(2) the force of the table pushing on the book

(3) the force of the book pushing on the table

(4) the force of the book pulling on the earth

Which two forces form an "action-reaction" pair that obeys Newton's third law?

• 1 and 2

• 1 and 4

• 3 and 4

• 1 and 3

Which of the following statements below best differentiate Static and kinetic friction?

• Static friction is when the force exerted and normal force are equal, while kinetic friction is when normal force is greater than the force exerted.

• Static friction happens when you apply more force than the mass of the object, while kinetic friction happens when you apply less force.

• Static friction is when the object is at rest while kinetic friction when the object is moving.

• Static friction occurs when you exert force on object and it doesn't move, while kinetic friction is the friction experienced when object is moving.

If you use a horizontal force of 30.0 N to slide a 12.0 kg wooden crate across a floor at a constant velocity, what is the coefficient of kinetic friction between the crate and the floor?

• 0.25

• 0.26

• 0.15

• 0.16

A 2.0 kg box is at rest on the table. The static friction coefficient μ_s between the box and table is 0.40, and the kinetic friction coefficient μ_k is 0.20. Then, a 5.0 N horizontal force is applied to the box. What is the best estimate of the magnitude of the box’s acceleration?

 

• 9.8 m/s2

• 8.6 m/s2

• 0 m/s2

• 11 m/s2