Question

In the following cases state whether work done or not. Justify your answer 1. A student reads a book 2. The revolution of earth around the sun.

Answer 1

in both cases work done is equals to zero as we all know that work done equals to force × displacement but in the first case the student read the book there is no force applied in it therefore the net work done equals to zero and in the second case the revolution of earth around the sun is a periodic process and it repeats after every revolution and after one complete Revolution the net displacement of the Earth is zero therefore the work done buy the earth is equals to zero

Answer 2

1. A student reads a book.

No, work is done because student is doing mental work by reading but there is no physical displacement.

2. The revolution of the earth around the sun.

Work is done as the earth is revolving around the sun as the displacement has taken place.