Give a short answer to the question given below.
 
a. Explain why a lawn sprinkler rotates when water passes through it. Mention the law of motion involved.

b. Explain how a horse can pull a cart if action is always equal to reaction.
 
a. The working of the rotation of is based on .
 
As the water comes out of the nozzle of the sprinkler, an comes into play. So, the sprinkler starts rotating.

b. According to , When a horse pushes the ground, the ground a force on the horse in the direction. This force is friction force of the cart and it moves.