# physics

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A rocket of total mass 2580 kg is traveling in outer space with a velocity of 111 m/s. To alter its course by 32.0 degrees, its rockets can be fired briefly in a direction perpendicular to its original motion. If the rocket gases are expelled at a speed of 1560 m/s, how much mass must be expelled?

• physics -

you want the velocity in the direction perpendicular to be 111sin32

Wouldn't one need the mass of the rocket gases expelled? normally this would be a mass burn rate (kg/sec). You certainly can't use the mass of the rocket as the mass of the gases.

Massgasses*velocitygases=massrocketremaining*velocity change rocket.

• physics -

this is also what my instructor said for this problem: the component of the final velocity in the direction of the original velocity vector remains unchanged for both the rocket and the gas.

• physics -

Of course that is true, what does that have to do with my question? One has to work the momentum change perpendicular to the original velocity vector. I said that, your instructor said that. But you still need the mass of the gas expelled, if you are going to do a momentum change.

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