# Homework Help: Work done by elevator

1. Nov 14, 2007

### NewJersey

A 4500kg elevator moves upward 10m in a times of 3.8s
a) The minimum work done by the motor is
b) The minimum motor power rewuired is

a W=F* X
So F= m*a , that 4500kg * 3.8s = 171,000

therfore P= 171,000/10 = 17,100

Is this right?

2. Nov 14, 2007

### firefly_1

You have the right equation for work however since the elevator is moving at a constant velocity and its direction doesn't change, there actually is no acceleration present.

Something to consider is that because the elevator is moving in the y-direction, gravity also has an affect on the forces that are acting on it. Therefore, to be able to move vertically, the elevator has to have a force equal to or greater than its weight (not mass). Weight is equal to its mass times gravity. Therefore, your equation would look like this: W = (mass)(gravity)(distance travel)

Hope this sets you on the right track.

3. Nov 14, 2007

### NewJersey

So it will be W= (4500kg)(9.8)(10) = 441,000