# Power developed

1. Dec 5, 2009

### Dark Visitor

A jet engine develops 1 * 10^5 n of thrust in moving the airplane forward at a speed of 900 km/h. What is the power developed by the engine?

I thought I needed to convert 900 km/h to m/s, so I did and I got 15000 m/s.

The only equation I see to use for this is:

P = Fvcosθ

When I used the equation, I got:

P = Fv
= (1*105)(15000 m/s)
= 1.5 * 109

I know I went wrong somewhere because it is multiple choice and that wasn't any of the answers. Please help me see my error(s) and help me get it right. I need this done a.s.a.p. by tomorrow. Thanks.

2. Dec 5, 2009

### rootX

How many seconds are there in one hour?

3. Dec 5, 2009

### denverdoc

900km/hr= 900000m/s divide by 3600 sec/hr and you get what?
Edit: sorry rootx, missed your response.

4. Dec 5, 2009

### Dark Visitor

My mistake. I completely missed that.

900000 m/h /3600 s = 250 m/s

And then I multiply that by the thing I had before:

P = Fv
= (1 * 105 N)(250 m/s)
= 250000 W
= 25 MW

Thanks guys. I got too much going on in my mind right now.