Question

A rocket works on the principle of
A. conservation of mass
B. conservation of energy
C. conservation of linear momentum
D. none of these

Answer 1

Hint: You could think of the core reason for the propulsion of a rocket. During the event of rocket propulsion, the rocket which is first at rest burns the propellants it carries. These propellants that have both as well as velocity are burned and ejected and as the resultant of this the rocket is pushed forward. Now, we know what principle is behind this.

Complete step by step solution:
In the question, we are asked to find the principle of working of a rocket.
Everybody knows that rockets get lifted up by burning of the fuel gases and propellants. These propellants that have both mass as well as velocity are getting ejected which thereby aids in the lifting up of rockets. This process could be considered as an application of Newton’s third law of motion which states that for every action there is an equal and opposite reaction. That is, the action here is the ejection of burned propellants backwards and as a resultant of this process, the rocket is getting pushed forward which is the reaction here. Since the action and reaction takes place in opposite directions, they are called opposite to one another.
The basic principle behind this process of rocket propulsion is however the conservation of linear momentum. Certain momentum is created as the result of rocket ejaculating gases backwards and in order to balance this momentum the rocket is pushed forward and hence, the linear momentum is conserved in this process. Therefore, we find that a rocket works on the principle of conservation of linear momentum.

Hence, option C is found to be the right answer.

Note:
We have both liquid rockets as well as solid rockets. The liquid rockets are the ones where the propellants are stored as liquids which get pumped to the combustion chamber of the nozzle where it gets burned and in solid rockets, they are solids packed into a solid cylinder. These propellants don't get burned at normal temperature but are provided with an external source of heat to aid the combustion process.