Question

Describe one "Newton's third law pair" of forces involved in the following situations; in each case state the object that each force acts on, the type of force and direction of force (a) you step on someone's toe (b) a car hits a brick wall and comes to rest (c) a car slows down by applying the brakes (d) you throw a ball upwards into the air

Answer 1

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)