Question

Ex. #17. In the previous chapter, rocket propulsion was explained in terms of Newton's third law. That is, the force hat propels a rocket is from the exhaust gases pushing against the rocket, the reaction to the force the rocket exerts on the exhaust gases. Explain rocket propulsion in terms of momentum conservation.

Answer 1

Rocket propulsion utilizes the principle of momentum conservation. The rocket moves forward by exerting a large backward force on the gas in the combustion chamber, which in turn exerts a large forward reaction force, propelling the rocket. Momentum conservation ensures the rocket's momentum changes by an equal amount in the opposite direction leading to its forward motion.

Step-by-step explanation:

Rocket propulsion in terms of momentum conservation utilizes the principle, wherein the momentum of the system remains constant unless acted upon by an external force. This means that as a rocket propels upwards, the momentum of the exhaust gases moving downwards is equal to the momentum of the rocket moving upwards.

Let's explore this further. Rockets move forward by expelling gas backward at high velocity. This means the rocket exerts a large backward force on the gas in the rocket combustion chamber, hence, the gas exerts a large reaction force forward, pushing the rocket. This reaction force is called thrust.

The conservation of momentum plays a vital role in this process. As the rocket engines operate, they are continuously ejecting burned fuel gases. This expelled gas carries mass and velocity, thus it carries momentum. By momentum conservation, the rocket's momentum changes by an equal amount but in the opposite direction, leading to the forward motion of the rocket.

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