PRACTICE ANOTHER A 78.0-kg person stands on a scale in an elevator. What is the apparent weight in each of the following situations?

Question

(a) when the elevator is accelerating upward with an acceleration of 1.00 m/s²

(b) when the elevator is moving upward at a constant speed

(c) when the elevator is accelerating downward with an acceleration of 1.80 m/s²

Answer 1

In all situations, the weight it balanced by the normal reaction force.

The normal reaction force depends on whether the elevator is is accelerating. An upward acceleration increases the reaction force and a downward acceleration does the opposite.

The man of mass m weighs mg when the elevator is stationary or moving at constant velocity.

The same man weights mg + ma when the elevator accelerates upwards and mg - ma when it accelerates downward.

Practically one can feel weightlessness if the downward acceleration exceeds a certain amount.