Question

what is no work force

Answer 1

There are many important examples of forces which do no work because they act perpendicular to the motion. For circular motion, the centripetalforce always acts at right angles to the motion. It changes the direction of the motion, but it does no work on the object. 

Answer 2

A force with no motion or a force perpendicular to the motion does no work. Case 1 : When a force is exerted on an object which does not move,no work is done on the object. Explanation : No matter how hard or how long you have pushed, if the object does not move, then you have done no work on the object. It is sitting still in the same place! Why then do you feel fatigued (as well as frustrated, etc. ). The resolution to this dilemma comes in considering that when your muscles are used to exert a force on something, the individual muscle fibers are in a continual process of contracting and releasing to maintain the net collective result of a steady force on an external object