Consider looking into Newton's second and third laws, especially as to how they relate to thrust from jet and rocket motors.
Second law is, generally, f = m.a , and the f is thrust.
Third law (again, generally) is for every action there is an opposite reaction; and, for straight line thrust in one direction, there is force in the opposite direction.
Any physicist reading this is welcome to make corrections and amplifications, btw.
Again w physics, there is lots to a turbojet engine... compressor stages, spools, ignition cans, turbines...Some aviation museums have very nice cutaways.
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F is the net force on the object, or aircraft from all sources. This includes thrust, gravity, and the "force of the air on the wings".
Typically, for a plane in level flight, the horizontal component of the force is taken to comprise the thrust and the drag, which must be equal and opposite at constant speed. The vertical component component comprises lift and the force of gravity, which must likewise be equal and opposite in level flight.