Question

Water sprinkler used for grass lawns begins to rotate as soon as the water is supplied. Explain the principle on which it works.

Answer 1

Water-sprinkler is based on the Newton's third law of motion i.e., “To every action, there is an equal and opposite reaction". 

A stream of water comes out of the nozzle of sprinkles with a force. The reaction force acting in the opposite direction, makes the sprinkler rotate.