1. Draw a free body diagram for the following situations:

a) A car is moving at constant speed on highway;

b) A car is accelerating to enter a highway;

2. A dockworker loading crates on a ship finds that a 20-kg crate, initially at rest on a horizontal surface, requires a 75-N horizontal force to set it in motion. However, after the crate is in motion, a horizontal force of 60 N is required to keep it moving with a constant speed.

Find the coefficient of static and kinetic friction between crate and floor.

3. A 300-kg crate is placed on an adjustable inclined plane. As one end of the incline is raised, the crane begins to move downward. If the crate slides down the plane at constant speed when the incline angle is 25°, what is the coefficient of kinetic friction between ramp and crate?