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Computer drawing of a rocket engine demonstrating Newton's Third Law of Motion.

Sir Isaac Newton first presented his three laws of motion in the "Principia Mathematica Philosophiae Naturalis" in 1686. His third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal and opposite force on object A. Notice that the forces are exerted on different objects.

In aerospace engineering, the principal of action and reaction is very important. Newton's third law explains the generation of thrust by a rocket engine. In a rocket engine, hot exhaust gas is produced through the combustion of a fuel with an oxidizer. The hot exhaust gas flows through the rocket nozzle and is accelerated to the rear of the rocket. In re-action, a thrusting force is produced on the engine mount. The thrust accelerates the rocket as described by Newton's second law of motion.

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Rocket Propulsion Activity: Grade 9-10
Fundamental Terminology: Grade 10-12
Hero Engine: Grade 6-10
Rocket Car: Grade 6-10
Rocket Pinwheel: Grade 6-10
Newton Car: Grade 10-12

Related Sites:
Rocket Index
Rocket Home
Beginner's Guide Home


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Editor: Tom Benson
NASA Official: Tom Benson
Last Updated: May 13 2021

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