BEST PRACTICE Friction

Graphs of kinetic friction versus normal force of different surfaces are shown. Which surface has the highest coefficient of kinetic friction?

• A

• B

• C

• All the same.

A graph of static friction versus normal force is shown. The coefficient of static friction is most nearly

• 0.5

• 0.5 N

• 2

• 2 N

A force of 40.0 N accelerates a 5.0-kg block at 6.0 m/s² along a horizontal

surface. How large is the frictional force in newton? Express the answer in whole number. No need to write the unit.

A force of 40.0 N accelerates a 5.0-kg block at 6.0 m/s² along a horizontal

surface. What is the coefficient of kinetic friction? Express the answer in two significant figures.

A 225-kg crate is pushed horizontally with a force of 450 N. If the coefficient of

static friction is 0.25 and the coefficient of kinetic friction is 0.20, which of the following will happen to the crate?

• The crate will not move.

• The crate will move at constant velocity.

• The crate will move with constant acceleration.

• The crate will move at changing acceleration.

A 225-kg crate is moved by pushing it horizontally with a force of 710 N. If the coefficient of kinetic friction is 0.20, what is the friction force (in newton) acting on the crate? Express the answer in whole number. No need to write the unit.

A 225-kg crate is moved by pushing it horizontally with a force of 710 N. If the coefficient of kinetic friction is 0.20, what is the acceleration (in m/s²) of the crate? Express the answer in two significant figures. No need to write the unit.

A sled of mass 50.0 kg is pulled along flat, snow-covered ground. The static

friction coefficient is 0.30, and the kinetic friction coefficient is 0.10. What force will be needed to start the sled moving?

• 500 N

• 150 N

• 50 N

• 350 N

A sled of mass 50.0 kg is pulled along flat, snow-covered ground. The static

friction coefficient is 0.30, and the kinetic friction coefficient is 0.10. What force will be needed to to keep the sled moving at a constant velocity?

• 500 N

• 150 N

• 50 N

• 350 N

A sled of mass 50.0 kg is pulled along flat, snow-covered ground. The static

friction coefficient is 0.30, and the kinetic friction coefficient is 0.10. Once moving, what force must be applied to the sled to accelerate it at 3.0 m/s²?

• 100 N

• 150 N

• 50 N

• 200 N