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

A rocket engine has an exhaust velocity of 20,000 m/sec. The mass flow (dm/dt) rate is 1 milligram per second.

a) What is the thrust produced by the engine?

b) The engine propels a 200 kg space craft. What change in velocity is achievable by running the engine continuously for one solid year?

note1: assume a constant mass for the system.

note2: One year = 31.56 x 10^6 seconds.

2. Relevant equations

Thrust = -Ve*(dm/dt)

Change in velocity = V - Vo = Ve*(ln Mo/M)

3. The attempt at a solution

a) Thrust = 20000m/s *(.000001kg/s) = .02N

b) 20000*(ln 200kg/31.56kg) = 36928.6 m/s^2

My question: Part A I believe is right but part b I am having trouble believing. Should I just keep it simple since the mass is constant at 200 kg? Thus giving a new equation which would be

a = (Thrust - W)/M

which is (.02N - (200kg*9.8m/s2))/200kg = 9.79m/s^2

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# Homework Help: Velocity change by running engine for 1 year

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