Question

If action is always equal to the reaction, explain how a horse can pull a cart?

Answer 1

when a horse pulls a cart the force exerted by a horse is much much greater than the force exerted by cart...and hence the net force is in direction of horse so the cart moves..

Answer 2

The amount of work done is directly proportional to the mass of the body. The same amount of forces act on different bodies to produce different amounts of work done.