Question

A rocket has a mass of 20000 kg of which 16000 kg is fuel. The rocket engine can exhaust fuel at the ite of
200 kg/s with an exhaust velocity of 3000 m/s relative to the rocket. Find the net force acting on the rocket 10
second after blast off [Take g = 10 m/s']
1) 4.2x10'N
2) 6x10'N
3) 1.8x10'N
4) zero​

Answer 1

Answer:

Given, fule consumption rate,

dm/dt= 200kg/sec

Exhaust velocity of gas w.r.t. rocket

vgr= 3000m/s

By using second law of Newton-

F external = Rate of change of linear momentum

dp/dt = 0 = 0 d/dt (mv) = 0

V dm/dt = (m dv/dt) - Thrust force

V= velocity of gas w.r.t. rocket

Thrust = vgr dm/dt = 3000X 200

= 1.8X10'N

so option 3 is correct answer.