4. Energy in a system may take on various forms (e.g. kinetic, potential, heat, light). The
law of conservation of energy states that energy may neither be created nor
destroyed, only altered to the other form energy. Therefore the sum of all the
energies in the system is a constant.
The most commonly used example is the pendulum:
The formula to calculate the potential energy is :
PE = m.g.h
PE : Potential Energy (J)
m : mass (kg)
g : acceleration of gravity (m/s2 )

5. The mass of the ball = 10kg
The height, h = 0.2m
The acceleration due to gravity, g = 9.8 m/s^2
Substitute the values into the formula and you get:
PE = 19.6 J (J = Joules, unit of energy)

6. The position of the blue ball is where the Potential Energy (PE) = 19.6J while the Kinetic
Energy (KE) = 0.
As the blue ball is approaching the purple ball position the PE is decreasing while the
KE is increasing. At exactly halfway between the blue and purple ball position the PE =
KE.
The position of the purple ball is where the Kinetic Energy is at its maximum while the
Potential Energy (PE) = 0.
At this point, theoretically, all the PE has transformed into KE> Therefore now the KE
= 19.6J while the PE = 0.
The position of the pink ball is where the Potential Energy (PE) is once again at its
maximum and the Kinetic Energy (KE) = 0.

7. We can now say and understand that:
PE + KE = 0
PE = -KE
 The sum of PE and KE is the total mechanical energy:
Total Mechanical Energy = PE + KE
NOTE: This is with the absences of outside forces such as friction.
Using our common sense we know that it's impossible for the pendulum
to swing higher than the height h without giving it a push yourself. If there
was no friction, the pendulum would swing back and forth forever
because of the law of conservation of energy.