Model rocket engines are sized by thrust, thrust duration, and total impulse, am

Question

Model rocket engines are sized by thrust, thrust duration, and total impulse, among other characteristics. A size C5 model rocket engine has an average thrust of 5.26 N, a fuel mass of 12.7 g, and an initial mass of 25.5 g. The duration of its burn is 1.90 s.

(a) What is the average exhaust speed of the engine?
m/s

(b) If this engine is placed in a rocket body of mass 46.0 g, and if the rocket is fired in outer space, what is the final velocity of the rocket? Assume the fuel burns at a constant rate.
m/s

Explanation / Answer

A. vex = impulse/mass = 5.26*1.9/0.0127 = 786.93 m/s B. Per the Tsiolkovsky rocket equation, delta-v = vex*ln(mi/mf) = ln(77.5/(77.5-12.7)) = 140.8 m/s

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