# Elevator jump problem

1. Apr 25, 2014

### MARS

Okay, so I know that if you are in a free falling elevator and you jump up you will hit the ceiling, something you could not do in an elevator that was still. But if the elevator was falling at a constant velocity, say 50 miles per hour, when you jump up will you also hit the ceiling because you are falling faster than 9.8m/s or will you jump the same height you did in a still elevator or an elevator moving at a constant velocity less than 9.8m/s? Keep in mind that the elevator is going 50 miles per hour at a constant velocity not accelerating like in a free fall.

2. Apr 25, 2014

### maajdl

Do you mean 9.8m/s² ?
The velocity has absolutely no effect on your jump capacity.
It is the acceleration of the elevator that changes you jump capacity.

3. Apr 25, 2014

### MikeGomez

I Agree with maajdl.

You would weigh the same, and if you could not jump high enough to reach the ceiling of the elevator when it was standing still, then you would not be able jump high enough to reach the ceiling when it is moving. The two situations are exactly equivalent. Even the tidal forces would be the same.

In fact, if you did not know whether or not you and the elevator were moving inertially or standing still (i.e. no noise, no rocking, etc.), then from inside the elevator there would be no experiment that you could perform which would allow you to determine that.

Last edited: Apr 25, 2014
4. Apr 25, 2014

### dauto

What makes you think the speed of 9.8 m/s is relevant to that question?

5. Apr 25, 2014

### sophiecentaur

It is hard to accept that you would be totally unaware if the lift were travelling downward at uniform velocity - it is not intuitive. This, I think, is because we never (very seldom) actually experience the situation in a form that we recognise. But you can prove it if you take a spring balance and a 1kg mass with you, next time you go in a lift. The mass will register 1kg all the time the lift is moving at steady speed, the 'weight' will change at the start and finish, whilst the lift is accelerating (+ or -). Take a nice long lift journey - like in the Shard or Empire State, where end effects are only a small part of the trip.