Kinetic & Static Friction (College Board AP® Physics 1: Algebra-Based): Exam Questions

State the two consequences of having kinetic friction present between two surfaces in contact when one surface moves over the other.

Identify whether the force of kinetic friction between two surfaces depends on the size of the contact surface area. Give a reason for your answer.

It is possible to calculate the magnitude of the kinetic friction acting between two surfaces.

State the equation used to calculate the magnitude of the kinetic friction.

Identify the units of the coefficient of friction. Give a reason for your answer.

A box is being pulled along a horizontal table by a parallel force of . The coefficient of kinetic friction is .

Calculate the kinetic friction acting on the box.

A different box of mass is now being pulled along a horizontal table by a parallel force of . The box accelerates at .

Determine the magnitude of the kinetic frictional force acting on the box during this motion.

The box in part (b) suddenly stops moving, but the applied force remains the same. Predict how this affects the magnitude of the friction now acting on the box. Give a reason for your answer.

Indicate whether the following statements are true or false. Give the correct version of any false statements.

1. Static friction occurs between the contact forces of two objects that are not moving relative to each other

2. Static friction is present on an object whether it is stationary or moving

3. Static friction acts in the same direction as the applied force

A forward force is applied to and then eventually moves a heavy object along a horizontal surface where friction is present. Describe how the magnitude of the static friction changes to get the object to begin to move.

When the object described in part (a) moves initially, it seems to slip suddenly.

i) Suggest why this is the case.

ii) Suggest whether more or less force is required to keep an object moving than to initially make it move.

iii) Suggest a suitable inequality in terms of appropriate symbols for the relationship between kinetic and static friction.

The object in part (a) is made heavier. Describe how this affects the magnitude of the forces involved.

A box is resting on a horizontal surface. The coefficient of static friction between the box and the surface is .

Calculate the maximum force that can be applied horizontally before the box begins to move.

The coefficients of kinetic and static friction are not equal. Identify whether the coefficient of kinetic or static friction is greater. Give a reason.

Define the terms slipping and sliding.

Identify the type of friction applied to an object that is rolling. Explain why this is the case.

Describe what happens to an object when it is slipping.