# Homework Help: Need help with a question on Newtons Law's of Motion.

1. Jun 29, 2004

### nelone

An elevator is moving upward with an acceleration of 1.0 m/s2. The total mass of the elevator and the passengers is 800kg. I need to find the tension in the elevator cable assuming g=32ft/s2. Need help, beginner in physics. Thanks!

2. Jun 29, 2004

### chroot

Staff Emeritus
Draw a free body diagram of the elevator and figure out the magnitude of the total force, applied by the cable, that is required to make it accelerate upwards at 1 m/s. That's the tension in the cable.

- Warren

3. Jun 30, 2004

### KnowledgeIsPower

Forces acting downwards are : Gravity (800g)
Forces acting upwards are : Tension.

Resolving forces and acceleration:
F = ma
T - 800G = 800x1
T = 800 + 800G

I never ever work in feet and can't believe they've given it to you in the form ft/s^2, is this an age old textbook or something? Personally i don't know the feet to m conversion but if gravity is 9.8m/s/s.
T = 8640N

4. Jun 30, 2004

### nelone

Thank you very much

5. Jun 30, 2004

### chroot

Staff Emeritus
KnowledgeIsPower:

Please refrain from giving actual numerical answers to homework problems. It is much more constructive pedagogically to explain the method for solving the problem, but leave the actual numerical solution to the student.

- Warren