Topic 9: One-Page Revision Sheet

Chapter 3: Work, Energy & Power – One Page Revision

1. Work

Work is said to be done when a force applied on a body produces displacement in the direction of the force.

Formula: W = F × s

SI Unit: Joule (J)

Types of Work

• Positive work – force and displacement in same direction
• Negative work – force and displacement in opposite direction
• Zero work – no displacement or force ⟂ displacement

2. Energy

Energy is the capacity of a body to do work.

SI Unit: Joule (J)

Forms of Energy

• Mechanical energy
• Heat energy
• Light energy
• Sound energy
• Electrical energy
• Chemical energy
• Nuclear energy

3. Kinetic Energy

Energy possessed by a body due to motion.

Formula: KE = (1/2) m v²

Depends on mass and square of velocity.

4. Potential Energy

Energy possessed by a body due to position.

Formula: PE = m g h

5. Work–Energy Theorem

Work done by the net force on a body is equal to the change in its kinetic energy.

W = KE_final − KE_initial

6. Law of Conservation of Energy

Energy can neither be created nor destroyed, but it can be converted from one form to another.

Mechanical Energy = KE + PE (constant in absence of external force)

7. Power

Power is the rate of doing work.

Formula: P = W / t

SI Unit: Watt (W)

Relation: P = F × v

Commercial Unit of Power

Horsepower (hp)
1 hp = 746 W

8. Important CET Points

• Numericals from KE, PE, Work–Energy theorem
• Energy conversion based MCQs
• Power formula and unit conversion
• Use g = 10 m/s² unless stated otherwise