# Homework Help: Power Cable Question

1. Jul 19, 2006

### webren

Hello,
I solved the first part of this problem, but I am a little stuck with finding the second part, which deals with power.

"A skier of mass 70.0 kg is pulled up a slope by a motor-driven cable. (a) How much work is required to pull him a distance of 60.0 m up a 30 degree slope (assumed frictionless) at a constant speed of 2.00 m/s? (b) A motor of what power is required to perform the task?"

In solving for part (a), I drew a free-body diagram and figured out what my x and y force components were:
Fx = -mgsin(30) = 0 (constant speed, so no acceleration)
Fy = n - mgcos(3) = 0

therefore:
Fx = mgsin(30) = (70)(9.80)(sin(30)) = 343 N.

Because Work = F(displacement)(cos(theta)), we can issue that work is = (343)(60) which equals 20580 J or 20.6 KJ.

I understand that Power = work/time, but because there is no time given in this problem, how do we find part (b)?

Any suggestions would be appreciated. Thank you.

2. Jul 19, 2006

### neutrino

The skier is moving 60m at 2m/s.

3. Jul 19, 2006

### webren

Ah, of course. I figured it out. Thank you.