Question

A 5000 kg rocket is set for verticle firing .the exhaust speed is 800 m/s to give an initial upward acceleration of 20 m/s the amount of gas ejected per second to supply the needed thrust will be: ( g =10m/s square) a) 127.5 b)187.5 c)185.5 d) 137.5

Answer 1

mass of the rocket= 5000kg
acceleration on the rocket= (20+10)= 30 m/ s2
force on the rocket =(5000×30)= 150000N
so the amount of gas to be ejected per sec for the required thrust= 150000/800 = 187.5 kg/s

hope this helps. :)