Newton's third law pair states that:
"when an object A exerts a force on object B, object B exerts an equal and opposite force on object B"
Applied to this exercise:
(a) you step on someone's toe
The action-reaction pair in this situation is:
- The force of your feet on the other person toe (downward)
- The force the toe applied on your feet (upward)
(b) a car hits a brick wall and comes to rest
The action-reaction pair in this situation is:
- The force applied by the car on the wall (direction: towards the wall)
- The reaction force applied by the wall on the car (direction: towards the car)
(c) a car slows down by applying the brakes
An example of action-reaction pair in this situation is:
- The force of friction the tires exert on the road, that makes the car slow down
- The reaction force exerted by the road on the tires, which is also a force of friction
(d) you throw a ball upwards into the air
The action-reaction pair in this situation is:
- The force you apply on the ball when throwing it (direction: upward)
- The reaction force the ball exerts on your hand (direction: downward)
