Question

a 8000 kg rocket is set for vertical firing. if the speed of exhaust is 980m/sec. then how much gas be ejected per second in orders to supply the thrust which is needed to overcome the weight of the rocket

Answer 1

if your answer is different so take g=10,best of luck

Answer 2

80 kg gas is ejected per second in orders to supply the thrust which is needed to overcome the weight of the rocket.

Thrust is given as:

Thrust = Velocity × Gas ejected per second

F = V × $\frac{dm}{dt}$                                ...(1)

 

We know, Thrust = Mass of rocket × Acceleration due to gravity (9.8 ms⁻²)

= 8000 kg × 9.8 ms⁻²

= 78400 N

Putting the value of thrust as 78400N and V = 980m/s (from question), we get:

78400 = 980 × $\frac{dm}{dt}$

⇒  $\frac{dm}{dt}$  = 78400/980 = 80 kg/s

Required mass of gas ejected per second is 80kg