Question

A rocket of mass 5700 kg ejects mass at a constant rate of
15 kg/s with constant speed of

12 km/s. The acceleration of the rocket 1 minute

after the blast is (g 10 m/s2)

Answer 1

After 1 minute 900 kg of mass has been ejected from rocket (15kg/s). So remaining mass of rocket is 4800 kg.
Now force required to eject mass at rate 15kg/s with velocity of 12km/s = 15×12×1000=180×1000
Now same force will be acting on rocket ( Newton's law of action -reaction) in opposite direction to the gravity on rocket.
So acceleration a= ( F-mg)/m
$(180 \times 1000 - 4800 \times 10) \div 4800 =$
=27.5 m/s2.

Answer 2

A rocket of mass 5700 kg ejects mass at a constant rate of
15 kg/s with constant speed of

12 km/s. The acceleration of the rocket 1 minute

after the blast is (g 10 m/s2)