Rocket engines work by expelling gas at a high speed as illustrated in Figure P7.71. We...

Rocket engines work by expelling gas at a high speed as illustrated in Figure P7.71. We wish to design an engine that expels an amount of gas each second, and we want the engine to exert a force F = 20,000 N on a rocket. At what speed vg should the gas be expelled? Assume the mass of the rocket is very large.