Definition of Energy
Energy is the capacity to do work. It exists in various forms and can be transformed from one form to another. Energy is a scalar quantity.
SI Unit: Joule (J)
Formulas and Solved Examples
- Kinetic Energy (KE): KE = ½mv²
- Potential Energy (PE): PE = mgh
- Work-Energy Principle: Work Done = Change in Energy
Example 1:
Find the kinetic energy of a 2 kg object moving at 3 m/s.
Solution:
KE = ½ × 2 × 3² = ½ × 2 × 9 = 9 J
Example 2:
Calculate the potential energy of a 5 kg object at a height of 4 m.
Solution:
PE = 5 × 9.8 × 4 = 196 J
Types of Energy
- Kinetic Energy: Energy due to motion
- Potential Energy: Energy due to position or height
- Thermal Energy: Energy due to heat
- Chemical Energy: Stored in chemical bonds
- Electrical Energy: Due to electric charges or current
- Sound Energy: Energy carried by sound waves
- Light (Radiant) Energy: Energy carried by electromagnetic waves
- Nuclear Energy: Energy stored in atomic nuclei
Example:
A battery converts chemical energy into electrical energy to power a torch.
Energy Conversion Table
| Type of Energy |
Converter |
Converted To |
| Chemical Energy |
Battery |
Electrical Energy |
| Electrical Energy |
Bulb |
Light Energy |
| Electrical Energy |
Heater |
Thermal Energy |
| Kinetic Energy |
Generator |
Electrical Energy |
| Light Energy |
Solar Panel |
Electrical Energy |
| Chemical Energy |
Human Body |
Kinetic & Thermal Energy |
| Electrical Energy |
Speaker |
Sound Energy |