Potential Energy is the energy stored in an object due to its position or configuration. It is introduced in Class 9 Science Chapter 11 – Work, Power and Energy.
What is Potential Energy?
Potential energy is the stored energy of an object because of its position relative to other objects, internal stress, or configuration.
For example, water stored in a tank at a height has potential energy due to its elevated position.
Formula of Potential Energy
The most commonly used formula is:
\[ \text{Potential Energy (PE)} = mgh \]- m = mass of the object (in kg)
- g = acceleration due to gravity (9.8 m/s²)
- h = height above the ground (in m)
Explanation
The higher an object is placed, the more potential energy it has. This is because more work is done in lifting it against gravity.
If an object is raised to a height \( h \), then the force needed to raise it is equal to its weight: \( F = mg \)
Work done = Force × Displacement = \( mg \times h = mgh \)
This work gets stored as potential energy in the object.
Examples of Potential Energy in Daily Life
- Water stored in a dam (gravitational potential energy)
- A stretched rubber band (elastic potential energy)
- A book kept on a shelf
- A compressed spring
Numerical Example
Q: What is the potential energy of a 2 kg object placed at a height of 5 m?
Solution:
\[ PE = mgh = 2 \times 9.8 \times 5 = 98 \, \text{J} \]Answer: The potential energy is 98 joules.
Important Points to Remember
- Potential energy depends on height and mass.
- It is a type of stored energy.
- Measured in Joules (J).
- Formula: \( PE = mgh \)