Question

What is thrust?

Answer 1

Hint : A thrust is a kind of reaction force that is used by different kinds of machines to propel themselves. Thrust is often produced by expelling matter in one direction.

Complete step by step answer
Thrust is a kind of reaction force that is a consequence of Newton’s third law. Newton’s third law tells us that every action has an equal and opposite reaction. When a system expels mass in one direction, the expelled mass will exert a force in the opposite direction to its direction of flow and propel the system in the other direction.
Thrust is commonly used to describe the acceleration mechanism of airplanes and rockets. Airplanes use propellers on their wings or in front of them which suck air from the front of the plane and push it out backward. By Newton’s third law, the air that is pushed back will exert a thrust on the airplane pushing it forwards.
Reverse thrust can also be generated by airplanes by sucking air from its rear portion and expelling it out front which is often done during the landing of airplanes to slow down and come to a stop.
Similarly, in rockets, fuel is burned and the flames are released in the downwards direction. This expulsion of mass makes the rocket rise upwards due to the reaction force generated by this expelled gas.

Note
Thrust is usually thought of as a force that acts on a surface in a direction that is perpendicular to the surface causing it to move in one direction or other. Since thrust is a force, it is represented by the units of Newton in the SI system.