Suppose that the earth revolves around the sun in a perfectly circular orbit. Does the sun do any work on the earth?

Explanation

When the earth revolves around the sun in a perfectly circular orbit the force of the sun on the earth is along the radius while displacement of the earth is along the tangent to the orbit. Now in a circle, radius and tangent are always orthogonal i.e., angle between them at any point on the orbit is `90^(@)` and so,work done by the sun on the earth is zero.