Question

Give an example of a situation in which there is a force and a displacement, but the force does no work. Explain why it does no work.

a) Pushing a stationary car; no displacement
b) Lifting a box vertically; force perpendicular to displacement
c) Dragging a suitcase with constant speed; force opposite to displacement
d) Pulling a sled uphill; force parallel to displacement

Answer 1

In physics, work requires force and displacement in the direction of the force. No work is done when pushing against a stationary wall, or carrying a briefcase while walking, as the force is not in the direction of the displacement.

Step-by-step explanation:

Work, as defined in physics, is done when a force causes a displacement of an object in the direction of the force. An example of a situation in which there is a force and a displacement, but no work is done, can be illustrated by considering pushing against a stationary wall. Even though you are applying a force, there is no movement or displacement, hence no work is done according to the physics definition.

Another scenario could be when a force is exerted perpendicular to the displacement, such as carrying a briefcase at a constant height while walking forward. The force exerted by your hand on the briefcase is upwards (against gravity), while the displacement is forward. Since the displacement is at a 90-degree angle to the force, the work done is zero.