Newton's Third Law states that for every action, there is an equal and opposite reaction. Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force back on the first object. Examples given include a hand pushing on a wall, which causes the wall to push back with an equal force, and a rocket pushing exhaust gases out, which causes the gases to push back on the rocket with an equal force. While the forces are equal, the effect of the forces depends on the masses of the objects, with lower mass objects experiencing greater acceleration from the same force.

1. Newton’s Third Law Action and Reaction

2. You can’t touch without being touched! A force is part of an interaction between two things. Ex. Hand pushes on wall and wall pushes on hand. In every interaction, forces always occur in pairs. The interacting force pairs are equal in strength and opposite in direction. Ex. You push backward on the floor when walking, and the floor pushes you forward.

3. Newton’s Third Law Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. To every action there is always an opposed equal reaction. Ex. Rocket pushes on gas, gas pushes on rocket.

4. Action and Reaction on Objects of Different Masses The effect of the force pairs on different objects depends on their masses (b/c of Newton’s 2nd). Ex. When a cannon is fired, even though the forces on the cannonball and the cannon are equal and opposite, the mass on the cannonball is less than the cannon so its acceleration is much greater. The cannon’s mass is so much larger, it kicks back (recoils) with less acceleration.