Work is defined as force multiplied by displacement.
If something is hanging from a string, although there is a tension force in the string, there is no displacement of whatever mass is hanging on the string, as it is not moving anywhere, or being displaced from an initial position to a different position. Hence displacement is zero.
When the tension force is multiplied by a displacement of zero, the result is zero work done by the string.
yes this is possible if the object is moving in a circuluar motoin , means centripetal acceleration , because force is in the circular motoin but the distance is perpendicular to the force , means make a cos90 angle , which is zero .... :) , ,. may be there is also another way to explain but em not pretty sure
yeah gotta remember may be object in equilibrium..