Thrust
Thrust is a force produced by an engine or propulsion system that accelerates a vehicle, typically forward, or counteracts drag.
Newton's Third Law: A principle stating that forces between two bodies are equal in magnitude and opposite in direction. A propulsion system pushes matter backward, and the resulting reaction force pushes the vehicle forward.
Force: An interaction that changes an object's motion or shape, measured in newtons in the SI system. Thrust is one kind of force acting on a vehicle.
Aircraft: A vehicle designed to fly by gaining support from air or by reacting against it. Powered aircraft use thrust to overcome drag and maintain or increase speed.
Power: The rate at which energy is transferred or work is performed. Power measures an energy rate, not the force a propulsion system exerts.
Conservation of Momentum: A physical law stating that total momentum remains constant in an isolated system. Thrust changes vehicle momentum by transferring momentum to exhaust, surrounding air, or another medium.
Drag: A resistive force exerted by a fluid on an object moving through it. Thrust must balance drag for steady speed or exceed it for acceleration.
Spacecraft propulsion: Methods of producing motion in spacecraft, including chemical, electric, and sail-based systems. In space, propulsion changes a spacecraft's velocity without aerodynamic lift or road contact.
Torque: A measure of the rotational effect of a force about an axis. Torque turns shafts and wheels; thrust is a force directed along a vehicle's motion.
Rocket Engine: An engine that produces thrust by expelling high-speed exhaust, carrying its own propellant and oxidizer. It produces thrust without relying on atmospheric air.
Momentum: A quantity of motion equal to an object's mass multiplied by its velocity. Propulsion produces thrust by changing the momentum of a vehicle and its surroundings.