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May 6, 2016

# Homework Help: physics

Posted by beavis on Wednesday, February 15, 2012 at 5:01pm.

A rocket has a per-ignition mass of 1100kgs-1 producing a thrust of 10000N. How long after ignition of the fuel will the rocket lift off?
also explain how is it possible for a rocket to accelerate in space.
(i cant work it outt. i know it involves the rocket thrust equation some how, the newtons 2nd law and suvat's..) thank you
• physics - drwls, Wednesday, February 15, 2012 at 5:10pm

You must have misspelled and omitted something.

I assume you mean pre-ignition mass, not per-ignition mass, which makes no sense.

If so, what is the pre-ignition mass? The number you have provided is a mass flow RATE.

The rocket lifts off then the trust equals the weight. Use the initial mass and the mass flow rate to figure out when that happens.

• physics - beavis, Wednesday, February 15, 2012 at 5:18pm

i haveeee!! ive posted the right question again please look it up again if you have time :(