Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

With the engines off a space ship is cruising at a velocity of 230m.s It fires a rocket straight ahead at the enememy vessel. The mass of the rocket is 1300kg and the mas of the ship (not including the rocket) is $4\times10^6$kg. The firing of the spaceship brings the spaceship to a halt. What is the velocity of the rocket.

share|cite|improve this question

closed as off topic by Qmechanic, David Z Feb 19 '12 at 19:39

Questions on Physics Stack Exchange are expected to relate to physics within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.

4X10^6 sorry did not put 6 to the power in the question – Fosho Feb 19 '12 at 17:06
Use law of conservation of momentum. – Pratik Deoghare Feb 19 '12 at 17:12
is the momentum lost by the ship = to the momentum gained the rocket – Fosho Feb 19 '12 at 17:13
Momentum before firing = Momentum after firing. – Pratik Deoghare Feb 19 '12 at 17:17
Hi Fosho! If what you would really like to know is "Is the momentum lost by the ship equal to the momentum gained by the rocket?" then you should edit that into your question. That would make it a conceptual question and in that case I'll be happy to reopen it. However, in its current form, all you're doing is posting your homework question and asking for a solution, which is off topic according to our FAQ. – David Z Feb 19 '12 at 19:41

First, the system has momentum:

mass of rocket * velocity of rocket + mass of ship * velocity of ship

After firing, the momentum is:

mass of rocket * velocity of rocket + mass of ship * velocity of ship

but you have to sort out which velocities go where and when ;)

share|cite|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.