Question

If action is always equal to the reaction, Explain How a horse can pull a cart ???

Answer 1

According to Newton's third law ,every action has equal and opposite reaction.
The horse pushes backward on the ground, so the ground pushes forward with an equal force.Its totally the ground which allows a horse to pull Cart. By Newton's third law the cart must then exert an equal and opposite force on the horse. The horse pushes backward and the ground pushes forward...
Thats an action reaction pair...Horse is doing action and in return the ground is giving reaction resulting in the motion of horse and cart....

Hope it helps...

Answer 2

According Newton's Third law of motion , For every action force there is an equal and opposite reaction force.
Action= -Reaction.
Action force is exerted by horse on cart when horse pulls the cart.
Reaction force which will be equal and opposite force will be exerted by the cart on the horse.
if we have a look at forces acting on horses, horse will exert action force on the ground by its feet where as reaction force exerted by ground on horse makes the horse move forward.
note:
Here frictional force plays a very important role.
frictional force should be more than action force.
Let F be the force applied by horse.
f = frictional force.
Fnet =F- f
where from Second law, Fnet = ma
so, ma= F-f
So acceleration will be produced . which makes the cart move