September 29, 2023

Rocket: In the view of a Common Man and a Science Person

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View of a common man:

On a Diwali eve a person is bursting a rocket placing it in a bottle and lights it. Think of a rocket cracker which has the explosive on the top of a stick. When the thread is lighten up it reaches the explosive which gets burnt and propulsion occurs. Propulsion is nothing but moving upward. The person sees the sparkle of the rocket till the explosive lasts. Then the empty stick lands back to the ground. The little amount of explosive has the power to carry the rocket to such height happens due to the decreasing weight of the rocket during movement. This is the simple explanation of the rocket mechanism.

View of a Science Person:

Propulsion of rockets is based on the law of conservation of linear momentum as well as Newton’s III law of motion. Rockets are filled with a fuel (either liquid or solid) in the propellant tank. When the rocket is fired, this fuel is burnt and a hot gas is ejected with a high speed from the nozzle of the rocket, producing a huge momentum. To balance this momentum, an equal and opposite reaction force is produced in the combustion chamber, which makes the rocket project forward.

While in motion, the mass of the rocket gradually decreases, until the fuel is completely burnt out. Since, there is no net external force acting on it, the linear momentum of the system is conserved. The mass of the rocket decreases with altitude, which results in the gradual increase in velocity of the rocket. At one stage, it reaches a velocity, which is sufficient to just escape from the gravitational pull of the Earth. This velocity is called escape velocity.

Terms for reference:

The linear momentum measures the impact of a force on a body.

Law of Conservation of Linear Momentum: There is no change in the linear momentum of a system of bodies as long as no net external force acts on them.

Newton’s third law states that ‘for every action, there is an equal and opposite reaction. They always act on two different bodies’.



All future scientists reading here dream to fly a rocket or like a rocket…

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