Calculating Exhaust Gas Speed for a 4200kg Rocket Launch

AI Thread Summary
To calculate the exhaust speed for a 4200kg rocket accelerating at 4.0g, the total effective acceleration must include the force to overcome Earth's gravity, resulting in a total of 5g. The thrust equation used is Fthrust = (mass flow rate) x (exhaust speed). By applying the corrected total acceleration, the exhaust speed is calculated as 7400 m/s using the formula 4200kg x 5 x 9.8 / 28kg/s. The initial calculation was incorrect due to not accounting for the additional gravitational force. The discussion highlights the importance of considering all forces acting on the rocket during launch.
pbumper1
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Homework Statement


A 4200kg rocket is to be accelerated at 4.0g at take-off from the Earth.
If the gases can be ejected at a rate of 28 kg/s, what must be their exhaust speed?

Homework Equations



Fthrust=mv2-mv1/t2-t1

The Attempt at a Solution



Multiplied 4200kgx4x9.8/28kg/s=-5900
 
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Your work seems fine to me. Do you have any specific questions on this problem?
 
The answer is wrong and don't understand why it is?
 
I figured it out for future reference, since the rocket has to overcome 1g you add it to the 4g. You use the same equation. 4200x5x9.8/28=7400m/s
 
pbumper1 said:
I figured it out for future reference, since the rocket has to overcome 1g you add it to the 4g. You use the same equation. 4200x5x9.8/28=7400m/s


Good catch! Nice job.:smile:
 

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