Question

Name the principle on which a rocket works.

Answer 1

Hint : A rocket works by burning liquid fuel in its boosters and expelling out the gas from its exhausts. This provides momentum to the rocket which can push it in the upwards direction.

Complete step by step answer
A rocket works by expelling gases from its exhaust which is situated at one end of its body at a very high velocity. The gases, which are produced by burning liquid fuel, escape from the exhaust. The escaping gases have a very high speed and hence this translates to a very large momentum.
Now according to the law of conservation of momentum, a system where no external force is applied will conserve its net momentum. This implies that the momentum of the gases coming out from the bottom of the rocket will have to be compensated by moving the rocket in an upwards direction so that the net momentum of the system is zero.
Due to the principle of conservation of momentum the body of the rocket is pushed upwards. The momentum of the gases, as well as that of the rocket, is such that if we add both of them, the net momentum of the system will be zero, and hence the total momentum of the system will be conserved.

Note
We can also say that the rocket works on the principle of Newton’s third law which tells us that ‘Every action has an equal and opposite reaction’. The rocket will expel gases with force in the downwards direction in the atmosphere which will make the rocket experience a force in the upwards direction hence propelling it upwards.