A 1000-Kg Space Probe Is Motionless in Space

Multiple Choice

A 1000-kg space probe is motionless in space. To start moving, its main engine is fired for 5 s during which time it ejects exhaust gases at 5000 m/s. At the end of this process it is moving at 20 m/s. The approximate mass of the ejected gas is:

A) 0.8 kg
B) 4 kg
C) 5 kg
D) 20 kg
E) 25 kg