# Homework Help: Third Law of Motion Problem Finding average Force

1. Oct 24, 2009

### twisted

1. A 9800kg rocket is travelling east along a horizontal frictionless rail at a velocity of 11m/s. The rocket is then accelerated uniformly to a velocity of 22m/s in a time of 0.75s by the expulsion of hot gases. What is the average force at which the gases are expelled by the rocket?

2. Relevant equations

3.
Finding the net acceleration.
22 = 11+a(0.75)
18.333=a
Finding force.
F = 9800x18.33
F = 179634

What have I done wrong here?

2. Oct 24, 2009

### Delphi51

Welcome to PF, Twisted!
My calculator says 14.67 for that
22 = 11+a(0.75)
11 = .75*a subtracted 11 from both sides
a = 11/.75 = 14.67 divided both sides by .75

3. Oct 24, 2009

### twisted

Ugh, I can't believe I entered it into my calculator wrong. I got it right now. Thanks alot for the quick response!
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