Question

Earth revolves around the sun. Calculate the work done by the gravitational force, assuming its path to be circular.

Answer 1

Work done is equal to zero assuming earth revolves around the sun in a perfect circle.

As $Work=Force\ast Displacement\ast cos\theta$

Where $\theta$ is the angle between force and displacement .

In this case $\theta =90degree$

As centripetal force is involved where earth is pulled towards the sun and direction of motion at each point is tangential to the orbit and as tangent makes $90degree$ with radius $\theta =90degree$

$Cos{90}^o=0$

Thereby $F\ast S\ast cos90=F\ast S\ast 0=0$

HENCE NO WORK IS DONE .