Question

When a horse pulls a cart, what is the force that helps the horse move forward?

Answer 1

Hint: To find out that which force helps the cart to move when a horse pulls the cart, we will use the Newton’s third law motion that states that every action has an equal and opposite reaction and also consider the fact that forces always act in pairs in the nature.

Complete step-by-step solution:
To know the solution to the given question we will first discuss what is the third law of motion.
if an object exerts a force on another object, then the other object must exert a force of equal magnitude and opposite direction back on object A.
so, we can say that the forces always occur in pairs, which means one body cannot exert a force on another without experiencing a force itself. We sometimes refer to this law commonly as the action-reaction, where the force exerted on the object is the action and the force experienced as a consequence of the action is the reaction.
Therefore, we can say that Newton’s third law of motion states that every action has an equal and opposite reaction.
Let us apply Newton's third law of motion in the case of horse and cart so as to know what force makes the cart move.
Now, let us consider the given figure and find out the various forces acting,

In the given figure we can clearly see that the horse is moving in the forward direction and by the above action-reaction law we got to know that forces always act in pairs. So, as the horse exerts some force on the ground in backward direction, due to the action-reaction law of motion the ground gives some reaction back in the form of frictional force in the forward direction and thus making the cart move.
The force exerted by the ground that makes the cart move is the frictional force.

Note: By the solution of this question we can also say that this newton’s third law of motion also gives rise to the principle of conservation of motion which states that the momentum can neither be created nor be destroyed it can only be transformed from one form to another.