# Homework Help: Work & Power Question

1. Jan 21, 2014

### Speedking96

1. The problem statement, all variables and given/known data

The ski tow at a ski resort takes 1000 people per hour to a height of 500 m. The average mass of the skiers using this tow is 60 kg. In the normal operation of the ski tow, the energy lost to fictional forces is 60%.

How much power is required to run the ski tow?

2. The attempt at a solution

Power = (work) / (time)

= (mgh) / (time)

= ( (60*1000) ( 9.81) (500) ) / (3600)

= 81750 Watts.

However, it will need an additional 60% of Power.

Thus: 81750 * 1.60 = 130,800 Watts.

2. Jan 21, 2014

### Staff: Mentor

Careful. The energy lost to friction is 60% of the total provided. So what percentage of the total is 81750?

3. Jan 21, 2014

### BvU

If I were to do this one, I would reason: the 82 kW is the 40% remaining, so the required power is 100/40*82 kW = 205 kW.
I don't think a ski resort at sea level is such a success, but perhaps they mean: to a height 500 meter above the resort...

4. Jan 21, 2014

### Speedking96

Isn't it just the 60% of the energy required to reach 500 meters?

I don't understand why the 81750 Watts are only 40% of the required power.

Last edited: Jan 21, 2014
5. Jan 21, 2014

### Staff: Mentor

No. Friction is 60% of the total energy; The energy needed to raise the lift is thus 40% of the total. You have to find the total.

6. Jan 21, 2014

### Speedking96

Ah. I see. Thank you.