# Homework Help: What's the deal with elevators?

1. Sep 27, 2004

### r.l.newman

Could someone list or explain what exactly goes on when an elevator begins to accelerate and comes to a stop (both up and down) so that I can solve the problem below!! :yuck:

A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.88 of the personâ€™s regular weight. Calculate the acceleration of the elevator. Find the direction of acceleration.

2. Sep 27, 2004

### Staff: Mentor

Some things to consider. If there were no elevator, the only force on the person would be his weight. He would accelerate downward at g, of course. The floor of the elevator holds the person up by exerting a force, the so-called normal force. It is that force that the scale reads. If there is no acceleration, then the forces on the person add to zero and the scale reads a force equal to the person's weight. But if the elevator accelerates upward, it must push with a greater force; if it accelerates downward, a lessor force.

As always, consider all the forces acting on the person and apply Newton's 2nd law. In these problems only two forces act: (1) the person's weight, and (2) the normal force of the elevator floor.