Arocket of mass m is launched from the surface of an asteroid by being bombarded by a stream of dust that was mined from the asteroid. the dust is ejected upward from the surface of the asteroid at a constant rate dm/dt ≡ r, and with a constant speed vd with respect to the asteroid. the rocket absorbs the dust, which just builds up in a storage compartment. find the speed of the spacecraft as a function of time. ignore the eect of gravity from the low mass asteroid, and assume that the asteroid is not rotating