Question

Work done by a force on an object will be zero, if:

• A. The force is always perpendicular to acceleration of object.
• B. The object is at rest relative to ground but the point of application of force moves on the object.
• C. The force is always perpendicular to velocity of object.
• D. The point of application of force is fixed relative to ground but the object moves.

Answer 1

Answer: (B), (C)

The force is always perpendicular to velocity of object.

If the velocity and acceleration are not in same direction, work done by force perpendicular to acceleration will not be zero.
b) If the object is at rest no force can do work.
c) If force is perpendicular to velocity work done will be zero.
d) If the point of application of force is fixed relative to ground, the motion will not be due to that force.