Question

What is the SI unit of thrust?

Answer 1

Hint: Thrust is a reaction force which is formed due to the action of a force (in which a mass is accelerated) in the opposite direction. It forms due to the consequence of Newton’s Third Law. So, thrust is essentially a force which has the same magnitude and acts opposite to a certain force.

Complete step by step answer:
Many of us have seen a rocket taking off, or a motorboat cruising through a river or sea, all of these motions is due to thrust, when the rocket fires its engines, the exhaust gas fires down onto the ground which applies a force downwards as a result of this force acting downwards a reaction force known as the thrust is formed which propels the rocket upwards.
In the case of a motorboat, the blades of the boat apply a force on the water that pushes the water backwards, and the water applies a resultant thrust on to the boat, which is responsible for the movement of the boat.
In both cases, the thrust is formed as the resultant force due to the action of a force acting on a particular body. So, thrust is a force that is formed as a result of Newton’s action-reaction pair. So, it will have the same unit as the force, which is Newton (N).

Note: Newton’s Third law states that ‘For every action, there is an equal and opposite reaction’ or we can say that that, all forces between two objects exist in equal magnitude and in the opposite direction.
If we take the example of the apple and the earth, the earth applies a gravitational force on the apple which applies a downwards acceleration on the apple, at the same time due to a reaction force, the earth is also accelerated towards the apple, but due to the huge mass of the earth compared to the mass of the apple, the acceleration produced is negligible.