A horse pulls a cart along a flat road. Consider the following four forces that arise in this situation. (1) the force of the horse pulling on the cart (3) the force of the horse pushing on the road (2) the force of the cart pulling on the horse (4) the force of the road pushing on the horse Which two forces form an "action-reaction" pair that obeys Newton's third law?

(1) - (2)

and

(3) - (4)

Explanation:

Hi!

The Newton's third law states that for every action there's and equal and opposite reaction.

Lets us consider the first force:

(1) the force of the horse pulling on the cart

Therefore, its counterpart, will be a force of the cart pulling on the horse, which is actually:

(2) the force of the cart pulling on the horse

Analogously, the third force:

(3) the force of the horse pushing on the road

and the fourth force:

(4) the force of the road pushing on the horse

From a action reaction pair, since the former force acts on the road by the horse, and the latter on the horse by the road