JEE Physics — Key Concepts

Work, Energy and Power

If you push a brick wall until you sweat, physics says you have done absolutely zero work.

Work only happens when a force actually moves an object. We calculate it by multiplying the force applied by the distance moved in that direction.

Energy is simply the stored capacity to do this work. When you lift a heavy box, your muscles transfer chemical energy into gravitational potential energy.

Release the box, and that stored potential energy instantly transforms into kinetic energy as it accelerates downward. Energy is never lost; it just changes forms.

But wait, does it matter how fast you transfer this energy? That is where power comes in—it measures the speed of your work.

So, no displacement means zero work, energy is your stored budget, and power is how fast you spend it. What is your favorite energy transfer?