Physics XI Content

6. “The earth moving round the sun in an orbit is acted upon by a force; hence the work must be done on the earth by this force.” Do you agree with this statement?

Earth is revolving around the sun in a circular path. For it, a centripetal force is required which is provided by gravitational force between the earth and the sun.
We know,
 Work done = Fscosθ
Where F is gravitational force, ‘s’ is the displacement travelled by earth and ‘θ’ is the angle between them.

Since, force and motion of earth are perpendicular to each other, θ=90˚ and

Work done = Fscos90˚= 0.

Hence, there is no work done on the earth by this gravitational force.