# Homework Help: Power question

1. Nov 21, 2004

### steelcap

Hey everyone, just wondering if anyone can help me out with a homework question I'm having trouble with. I've been stuck on it for about 45 minutes now, any help will be appreciated. Thanks.

"A conveyor belt is driven by a motor rated at 60kW. Only 90% of the rated power is available for useful work. The coal is to be raised and deposited into a hopper 19.5m above. How many kilograms of coal can be delivered by this motor per minute?"

- Matt

2. Nov 21, 2004

### ek

If you use t = 60s, then find the mass through work/potential energy considerations.

$$P = \frac {W}{t}$$

$$W = mgh$$

$$P = \frac {mgh}{t}$$

$$m = \frac {Pt}{gh}$$

3. Nov 21, 2004

### check

Dont forget to forget to multiply the power by the motor's efficiency!