Answer
The force is the least when the elevator is accelerating downward, and the greatest when the elevator is accelerating upward.
Work Step by Step
When the elevator is accelerating downward, the weight of the crate exceeds the upward normal force because the net force is downward. With a small normal force, the friction between the crate and the floor is reduced.
When the elevator is accelerating upward, the weight of the crate is less than the upward normal force because the net force is upward. With a large normal force, the friction between the crate and the floor is increased.
