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A rocket of total mass 900 kg floats at rest in empty space…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A rocket of total mass floats at rest in empty space. It throws out of gas backwards at . Find the rocket's speed after this burst.
Need a reminder? The key ideaShow
With no outside force, the total momentum of a group of objects stays the same: . Give opposite directions opposite signs. Things that start at rest end with equal and opposite momenta.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Gas. backwards.
Step 2. Rocket. , so forwards.
Answer: About .
Watch out. Use the rocket's mass after the gas has left, .
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