Question

when a work done by a force is zero

Answer 1

work done =FXSXcosθ

so work done is depend upon force,distance and the angle of direction of force

i.e when the force of distane become zero the work done be zero

and when angle is 90 degrees
as cos 90 degrees= 0 so in these cases work done becomes zero

                                                         -thank you :)



                   

Answer 2

when displacement and force are perpendicular to each other......bcoz. work done=force * displacement cosß (cosß=0) when at an angle of 90°