Energy and Work for grade 8

1.Kind of energy :
1. Mechanical energy

a. Potential energy

b. Kinetic energy

2. Heat/thermal energy

3. Electric energy

4. Chemical energy

5. Sound energy
6. light energy

Source Energy

Slide 5

1.Solar energy

2.Wind energy

3.Water energy

4.Biogas energy

5.Geothermal energy

6.Petroleum and coal energy

7.Nuclear energy


Potential energy
Slide 7

Potential energy is influence by mass of the

object (m), height of the object to the earth

(ground) and earth gravitational acceleration

Mathematically, it is formulated by

EP = m x g x h

Ep = potential energy (Joule)

m = mass (kg)

g = gravitational acceleration (m.s-2)

h = height of the object (m)

Kinetic Energy
Is the energy an object possesses due to

the its motion.

The kinetic energy is formulated as follow :

Ek = 1/2 x m x v2

Ek = kinetic energy (Joule)

m = mass (kg)

v = velocity or speed (m.s-1)


Example :
A car move mass 1500 kg is travelling with

speed of 20 m.s-1. What is the kinetic energy

of the car ?

Mechanical energy is...

sum of potential energy and kinetic energy owned by the object.

Em = Ep + Ek

Example : swing

physics animation

I hope this animation help you to understanding the appropriate concept.