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rock33y

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## Homework Statement

A rocket for use in deep space is to have the capability of boosting a pay load ( plus the rocket frame and engine) of 3 metric tonnes to an achieved speed of 10000m/s with an engine and fuel designed to produce an exhaust velocity of 2000m/s.

a) How much fuel and oxidizer is req'd, b)and if a diff fuel and engine design could give an exhaust velocity of 5000m/s, what amount of fuel and oxzidier would be req'd?

## Homework Equations

P=P'

## The Attempt at a Solution

m1 = 3000 kg, v1= 0, v1' = 10 000m/s

m2 = ? kg, v2 = 0, v2' = 2000m/s

m1v1 + m2v2 = m1v1' + m2v2'

0 = m1v1' + m2v2'

-m1v1' / v2'= m2

-15 000 kg = m2

How is the mass negative :S

the answer at the back says "442 x 10^3 kg"

so I know I'm off by a lot... Our fizzicks teacher didn't teach us how to solve these problems, but I assumed it was a momentum problem.

Any help would be greatly appreciated. :)