Question

Which of the following need to be considered when the rocket operates:
(A): As the rocket consumes fuel at every instant, its mass goes on decreasing.
(B): The acceleration due to gravity changes continuously as the rocket ascends.
(C): The atmosphere offers resistance in the lower strata of atmosphere.

• A. A, B and C
• B. Only B and C
• C. Only C
• D. None of the above

Answer 1

The correct option is A A, B and C

As the rocket consumes fuel at every instant, the fuel is converted to gases and are thrown out of the rocket. Hence the fuel content gets lesser and lesser as the fuel burns. Thus the mass goes on decreasing.

When these gases are thrown out, they exert a force on the rocket and it gets propelled.

As per the equation, $force=mass\times acceleration$, lesser the mass, greater is the acceleration of the rocket. This point must be considered while studying the motion of the rocket.

The acceleration due to gravity changes continuously as the rocket ascends because, the downward gravitational force acting on any object becomes lesser and lesser as it goes away from the earth. Hence the net force acting on the rocket goes on increasing.

This point must also be considered

In the lower strata of atmosphere, its density is more. Hence it offers greater resistance to moving bodies. The rocket has to thus overcome this force of resistance at lower height. This decreases the net force acting on the rocket at lower height.