PhysicsLAB: Newton's Law of Motion: Friction

Refer to the following information for the next two questions.

A crate filled with delicious junk food rests on a horizontal floor. Only gravity and the support force of the floor act on it, as shown by the vectors for weight W and normal force N.

The net force on the crate is

zerogreater than zero

Evidence for this is ____.

Refer to the following information for the next three questions.

A slight pull P is exerted on the crate, not enough to move it.

A force of friction f now acts, which is ____ P.

less thanequal togreater than

This type of friction is called ____ friction.

staticsliding or kineticrolling

The net force on the crate is

zerogreater than zero

Refer to the following information for the next four questions.

The pull on the crate is increased until the crate begins to move. It is pulled with pull P so that it moves with constant velocity across the floor.

Friction f is ____ P.

less thanequal togreater than

This type of friction is called ____ friction.

staticsliding or kineticrolling

Constant velocitv means acceleration is

zerogreater than zero

The net force on the crate is ____ zero.

less thanequal togreater than

Refer to the following information for the next two questions.

Pull P is further increased and is now greater than friction f.

The net force on the crate is ____ zero.

less thanequal togreater than

The net force acts toward the right, so acceleration acts toward the

leftright

Summary Questions

If the pulling force P is 150 N and the crate doesn't move, what is the magnitude of the static friction, f?

If the pulling force P is 200 N and the crate doesn't move, what is the magnitude of the static friction, f?

If the force of sliding friction is 250 N, what force is necessary to keep the crate sliding at constant velocity?

If the mass of the crate is 50 kg and sliding friction is 250 N, what is the acceleration of the crate when the pulling force is 250 N?

If the mass of the crate is 50 kg and sliding friction is 250 N, what is the acceleration of the crate when the pulling force is 300 N?

If the mass of the crate is 50 kg and sliding friction is 250 N, what is the acceleration of the crate when the pulling force is 500 N?