Question

Water sprinklers used for grass lawns begin to rotate as soon as the water is supplied. It is based on which law?
A) Newton’s first law of motion.
B) Newton’s second law of motion.
C) Newton’s third law of motion.
D) First law of thermodynamics.

Answer 1

Water sprinklers are commonly used in irrigation systems to supply water in the form of rainfall. The sprinkler rotates to supply water across all areas of the grass lawn. The rotation is a response to the flow of water to it.

Complete step by step solution:
Step 1: Try to explain the procedure in which water is sprinkled by the water sprinkler.
Water from the pipes is supplied to the sprinkler. This sprinkler then sprays the water all around the grass lawn as it rotates. Newton’s third law of motion states that to every action there is an equal and opposite reaction. The water sprinkler works on the same principle. As soon as the water supplied to the sprinkler reaches its nozzle and it comes out of the nozzle, an equal and opposite force comes into existence. This force then causes the sprinkler to rotate so that water gets distributed uniformly across the grass lawn.
So we can conclude that the working of the water sprinkler is based on Newton’s third law of motion.

Hence the correct option is C.

Additional information: Newton’s third law of motion has many applications in our day-to-day life. Some instances where its applications are seen are when a person tries to swim or walk or simply lies on the bed. The swimmer pushes the water backwards and the water pushes the swimmer forward causing the swimmer to swim. A person walking simply pushes the ground backwards and the ground pushes that person forwards causing the person to walk. A person lying on a bed exerts a force equal to his or her weight. The bed then exerts a reaction force on the person so that the person does not fall through the bed.

Note: Newton’ first law is the law of inertia which states that a body will continue its state of motion or of rest until an external force acts on it. Newton’s second law introduces the concept of the momentum of a body. The first law of thermodynamics states that the heat supplied to a system is used in increasing its internal energy and to do useful work. So we can clearly rule out options A, B and D.