Introduction
Work is said to be done when a force applied on an object causes displacement in the direction of the force.
Energy is the capacity to do work.
Work
Conditions for Work to be Done
- A force must act on an object.
- The object must move in the direction of the force.
Formula:
Work=Force×Displacement
- SI unit of work: Joule (J)
- 1 joule = work done when a force of 1 N moves an object by 1 m.
Types of Work
- Positive Work: Force and displacement in same direction.
- Negative Work: Force and displacement in opposite directions.
- Zero Work: No displacement or force perpendicular to motion.
Energy
Energy exists in different forms.
1. Kinetic Energy
- Energy possessed due to motion.
- Formula:
KE=21mv2
2. Potential Energy
- Energy possessed due to position or shape.
- Formula:
PE=mgh
Mechanical Energy
- Sum of kinetic and potential energy.
Law of Conservation of Energy
Energy can neither be created nor destroyed, but it can be converted from one form to another.
Total energy of a system remains constant.
Power
- Rate of doing work.
- Formula:
Power=TimeWork
- SI unit: Watt (W)
- 1 watt = 1 joule per second.
Commercial Unit of Energy
- Kilowatt-hour (kWh)
- 1 kWh = 3.6 × 10⁶ J
- Used for measuring electrical energy consumption.
Important Applications
- Moving vehicles
- Falling objects
- Hydroelectric power plants
- Electrical appliances
Quick Short Q&A (Most Possible)
| Question | Short Answer |
|---|---|
| What is work? | Force causing displacement |
| SI unit of work? | Joule |
| What is energy? | Capacity to do work |
| Kinetic energy formula? | ½mv² |
| Potential energy formula? | mgh |
| Law of conservation of energy? | Energy cannot be created or destroyed |
| What is power? | Rate of doing work |
| SI unit of power? | Watt |
| Commercial unit of energy? | kWh |
| 1 kWh equals? | 3.6 × 10⁶ J |