posted by peyton on .
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?
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.
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.
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.