What are examples of Newton's third law of motion?


Quick Answer

A primary example that demonstrates Newton's third law of motion is a flying airplane, where two pairs of action-reaction forces influence its flight. Other examples include a jumping child, bouncing ball and a falling fruit.

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Full Answer

The English physicist and mathematician Sir Isaac Newton formulated three fundamental concepts concerning the movement of physical objects when various forces act on them. Newton's third law illustrates the interaction that occurs between two objects. For instance, when an object "P" exerts a force against object "Q," an equal and opposite force is always exerted by Q against P. These forces are referred to as action-reaction forces.

In a flying airplane, four types of forces are acting on it. The upward force pertains to the lift, which is opposite and equal to the weight of the air. This downward force that the air exerts against the wings of the craft actually creates the lifting force that makes the airplane fly. The backward force refers to the drag, which acts in the opposite direction to the forward thrusting force of the airplane.

When a child jumps, the legs exert a downward force against the ground, which is countered by the force exerted by the ground against the child's legs. This force enables the child to be pushed off from the ground and be suspended in the air for a few seconds. A similar scenario occurs when a ball is bounced on the ground. In the case of a falling fruit, the earth exerts a downward gravitational force against the tree branch where the fruit is hanging. An equal and opposite force is exerted by the branch against the earth to keep from falling. Eventually, gravity overcomes this upward force and the fruit drops to the ground.

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