Work, Energy and Power

5 min

Essential concepts, formulas, and units for competitive exams.

The Golden Rule

Work is done when a force produces displacement in its direction. Energy is the capacity to do work, while Power is the rate at which work is performed.

Why Study This?

Direct numericals on Work and Kinetic Energy are common in SSC and Railways.
Power units like Horsepower (746 W) are frequent MCQ targets.
Conceptual questions on Potential Energy appear in Police and State exams.

Memory Hooks

K.E. = Keeps Evolving (Motion energy: 1/2 mv²)
P.E. = Position Energy (Stored energy: mgh)
1 Horse = 746 Watts (Standard power conversion)

Quick Reference Table

Quantity	SI Unit	Formula
Work	Joule (J)	F × d cosθ
Power	Watt (W)	Work / Time
Kinetic Energy	Joule (J)	1/2 mv²

Visualizing Concepts

Work Done

(Force in action)

Force in action

Pushing a wall is zero work.

Potential

(Stored by height)

Stored by height

Water behind a dam has PE.

Kinetic

(Motion energy)

Motion energy

A speeding bullet has high KE.

Horsepower

(Engine strength)

Engine strength

1 HP equals 746 Watts exactly.

Exam Traps

Work is a vector quantity.Work is a scalar quantity.

Work has magnitude but no specific direction, even if force and displacement are vectors.

1 Horsepower = 1000 Watts.1 Horsepower = 746 Watts.

Don't confuse HP with KiloWatt (1000W). Exams always test this specific number.

Walking with load = positive work.Walking with load = zero work.

Work is zero because force (up) is 90 degrees to displacement (forward).

Test Your Knowledge

Q1.If the velocity of an object is doubled, its kinetic energy becomes:

Q2.What is the value of 1 Horsepower in Watts?

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