Potential Energy

Potential energy, in other words, is called stored energy.

There are many sorts of potential energy. Three main types are:

• Gravitational potential energy

• Elastic potential energy

• Chemical energy

Gravitational Potential Energy

When you lift an object from the ground, it gains gravitational potential energy. This energy stays the same until the object is moved upwards or downwards.

When the object is moved, the gravitational potential energy gets converted to other forms of energy, such as kinetic energy.

Equation:

GPE=M×G×HGPE = M \times G \times HGPE=M×G×H

Where:

• M = Mass (kg)

• G = Acceleration of free fall (universally accepted as 10 m/s210 \, m/s^210m/s2)

• H = Height gained (m)

Example 1:
Ball lifted to a height of 5 m, mass = 4 kg

GPE=4×10×5=200 joulesGPE = 4 \times 10 \times 5 = 200 \, \text{joules}GPE=4×10×5=200joules

Example 2:
Fridge lifted to a height of 6 m, mass = 40 kg

GPE=40×10×6=2400 joulesGPE = 40 \times 10 \times 6 = 2400 \, \text{joules}GPE=40×10×6=2400joules

Example 3:
Oven lifted to a height of 7 m, mass = 12 kg

GPE=12×10×7=840 joulesGPE = 12 \times 10 \times 7 = 840 \, \text{joules}GPE=12×10×7=840joules

Elastic Potential Energy

When a string is stretched, it stores energy in the form of elastic potential energy. The energy remains unchanged until the string’s length changes.

Equation:

E=12×k×(Δx)2E = \frac{1}{2} \times k \times (\Delta x)^2E=21​×k×(Δx)2

Where:

• k = Spring constant (N/m)

• Δx = Change in extension (m)

Example:
Spring length changes from 5 m to 10 m, k=0.5 N/mk = 0.5 \, N/mk=0.5N/m
Change in extension:

Δx=10−5=5 m\Delta x = 10 - 5 = 5 \, \text{m}Δx=10−5=5m E=12×0.5×52=6.25 joulesE = \frac{1}{2} \times 0.5 \times 5^2 = 6.25 \, \text{joules}E=21​×0.5×52=6.25joules

Chemical Energy

Chemical energy is the energy stored in the bonds of chemical compounds.

• When we eat, we store energy in the form of chemical energy in our bodies.

• During work, chemical energy is converted to heat and kinetic energy.