# Homework Help: Estimate the power required to operate the tow

1. Sep 4, 2007

### Edwardo_Elric

1. The problem statement, all variables and given/known data
A ski tow is operated on a 20 degree slope of lenth 300m. The rope moves at 12.0km/h, and power is provided for 70 riders at one time with an average mass per rider of 65kg. Estimate the power required to operate the tow.

2. Relevant equations
P = Work / t
P = F * v

3. The attempt at a solution
60kg * 70 riders = 4550kg
Solving for time:
V = 12km/h = 3.33m/s

t = d / V
= 300m / 3.33m/s
= 90.09s

P = (F * d) / t
P = ((4550kg)(9.8m/s^2)( 300m))/(90.09s)
= 148484.8485 watts

I dont see what is the angle used for
maybe for another component of force? or is it no use?

Last edited: Sep 4, 2007
2. Sep 4, 2007

### learningphysics

You need the acceleration along the slope to be zero to keep the riders moving at a constant velocity along the slope... The ski tow exerts a force along the slope.

Also, you can directly use F*v for power, instead of using time and distance...

3. Sep 4, 2007

### Edwardo_Elric

0 = F - wsin(theta)
F = (4550kg)(9.8m/s^2)sin(20) << so force

thanks

4. Sep 5, 2007

### learningphysics

yup. then using this force F*v gives power.