(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The first stage of a Saturn V space vehicle

consumes fuel at the rate of 47400 kg/s, with

an exhaust speed of 2820 m/s.

The acceleration of gravity is 9.8 m/s2 .

Calculate the thrust produced by these en-

gines.

Answer in units of N.

(part 2 of 2) 10.0 points

Note: You must include the force of gravity.

Find the initial acceleration of the vehicle

on the launch pad if its initial mass is 1.1 ×

107 kg.

Answer in units of m/s2.

2. Relevant equations

vrel*r= ma = thrust

3. The attempt at a solution

For the first part, I got 133668000 N, which is right. For the second part I divided the answer to the first part by the given mass. I got 12.51 m/s^2. Then to account for the acceleration of gravity, I subtracted 9.81 m/s^2 and got 2.3 m/s^2. However, that's not the correct answer. What am I doing wrong here? Can I not substract accelerations like that? It seems to me, I should be able to-- They're vector quantities acting in opposite directions.

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# Homework Help: Thrust problem

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