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Difficulty: HardNewton's Third Law (Action/Reaction)

In the context of Newton's Third Law of Motion, every action force has a specific, equal, and opposite reaction force acting on a different body. Match each described action force on the left with its exact corresponding reaction force on the right.

  • The downward aerodynamic force exerted by a hovering helicopter's rotor blades on the surrounding air.The upward aerodynamic lift force exerted by the surrounding air on the helicopter's rotor blades.
  • The upward magnetic pull exerted by an industrial crane's electromagnet on a piece of scrap steel.The downward magnetic pull exerted by the piece of scrap steel on the industrial crane's electromagnet.
  • The downward gravitational force exerted by the Earth's mass on a descending skydiver.The upward gravitational force exerted by the descending skydiver's mass on the Earth.
  • The forward mechanical force exerted by the internal walls of a fire hose nozzle on an exiting stream of high-pressure water.The backward mechanical recoil force exerted by the high-pressure stream of exiting water on the fire hose nozzle.

Answer

The correct pairings strictly follow the A-on-B / B-on-A rule, where the reaction force is always the exact same type of force exerted in the opposite direction by the receiving object back onto the originating object.
According to Newton's Third Law, forces always come in pairs. If body A exerts a force on body B, then body B simultaneously exerts an equal and opposite force on body A. The correct matches precisely swap the 'exerter' and the 'receiver' of the force while maintaining the identical fundamental type of force (gravitational, magnetic, aerodynamic, or mechanical).

Step-by-Step Solution

1
Analyze the action force to identify the two interacting bodies (Object A and Object B).
For example, in the skydiver scenario, Object A is the Earth and Object B is the skydiver.
Newton's Third Law strictly dictates that action and reaction forces must occur between two interacting objects.
2
Identify the type and direction of the force exerted by Object A on Object B.
The Earth exerts a downward gravitational force on the skydiver.
You must know the exact nature of the action force to find its true paired reaction.
3
Reverse the roles of the objects and the direction of the force to find the reaction.
The reaction must be Object B (the skydiver) exerting an upward gravitational force on Object A (the Earth).
Reaction forces are always equal in magnitude, opposite in direction, of the same type, and act on the opposing body.
4
Repeat this reversal process for all given scenarios and select the matching right-side items.
Helicopter on air pairs with air on helicopter; Magnet on steel pairs with steel on magnet; Nozzle on water pairs with water on nozzle.
This guarantees an accurate mapping of all Newton's Third Law pairs without falling for common distractors like balancing forces.

Key Concept

Newton's Third Law (Action/Reaction Pairs)
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Topics

Newton's Third Law (Action/Reaction)

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