Work, Energy and Power in Physics

What is Work?

In physics, work is done when a force causes an object to move through a distance in the direction of the force. Work is calculated using the formula: Work = Force × Distance (W = F × d). Work is measured in Joules (J). Importantly, if there is no movement, no work is done in the physics sense, even if a force is applied (e.g. pushing against a solid wall that doesn't move).

What is Energy?

Energy is the capacity to do work. It exists in many forms and can be transformed from one form to another, but according to the Law of Conservation of Energy, it cannot be created or destroyed — only converted from one form to another.

Forms of Energy

• Kinetic energy: the energy of a moving object. Formula: KE = ½mv² (where m = mass, v = velocity).
• Potential energy: stored energy due to an object's position or state. Gravitational potential energy formula: PE = mgh (where m = mass, g = gravitational acceleration, h = height).
• Chemical energy: stored in chemical bonds (e.g. in food, fuel, batteries).
• Thermal (heat) energy, electrical energy, and light energy are other common forms.

Energy Transformation

Energy constantly changes form. For example, a falling object converts potential energy into kinetic energy; a battery converts chemical energy into electrical energy; a light bulb converts electrical energy into light and heat energy.

What is Power?

Power is the rate at which work is done, or the rate at which energy is transferred. Power is calculated using the formula: Power = Work / Time (P = W / t). Power is measured in Watts (W), where 1 Watt equals 1 Joule per second.

Relating Work, Energy and Power

Work and energy are measured in the same unit (Joules) because doing work transfers energy. Power tells us how quickly that energy transfer or work happens — a more powerful machine does the same work in less time.

Real-Life Applications

Understanding work, energy and power helps explain how machines like engines and motors are rated, why climbing stairs quickly requires more power than climbing slowly (even though the work done is the same), and how electricity bills are calculated based on energy consumption over time.