Question

Q.what is the amount of work done by
a: the earth's gravitational force in keeping the moon in its circular orbit around the earth?
b: an electron moving with half the speed of light in empty space free of all forces and for from all matters?​

Answer 1

1. In this case work done is zero because force direction to the motion is perpendicular

thus W =F*S*cos 90degree

now W=F*S*0 (cos 90=0)

thus W =0

2. since all force is zero so the work done by electron will be zero

as we known that

W =F*S

F =0

then

W= 0

hope this help you