A crate rests on the bed of a flatbed truck. As the truck accelerates to the east, the crate moves with it without slipping. In what direction is the frictional force exerted by the bed on the crate?

A crate rests on the bed of a flatbed truck. As the truck accelerates to the east, the crate moves with it without slipping. In what direction is the frictional force exerted by the bed on the crate?

• A. Sideways
• B. To the East
• C. To the West
• D. There is no friction force, because the crate isn't sliding

Answer: (B)

When a surface accelerates, static friction provides the horizontal force that drags an object along with the surface. If the truck speeds up to the east and the crate doesn’t slip, the bed must push the crate forward to keep it moving with the bed. That push is friction, and it points in the same direction as the truck’s acceleration. So the frictional force from the bed on the crate is directed to the East.

When a surface accelerates, static friction provides the horizontal force that drags an object along with the surface. If the truck speeds up to the east and the crate doesn’t slip, the bed must push the crate forward to keep it moving with the bed. That push is friction, and it points in the same direction as the truck’s acceleration. So the frictional force from the bed on the crate is directed to the East.