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2
2
We know, v = u + 2as
2
⟹ v = 0 + 2ax = 2ax [As, velocity at A, u = 0]
Also, Kinetic energy, Ek = 1/2 mv
2
⟹ Ek =1/2 m × 2gx

⟹ Ek = mgx
Potential energy, Ep = mg (h – x)

So, total energy, EB = Ep + Ek
⟹ EB = mg (h − x) + mgx

⟹ EB = mgh – mgx + mgx

⟹ EB = mgh
At the end the body reaches the position C on ground.

At point C,
Potential energy, Ep = 0

Velocity of the body is zero here.

2
2
So, v = u + 2as
2
⟹ v = 0 + 2gh = 2gh
Kinetic energy, Ek = 1/2 mv
2
⟹ Ek = 1/2 x m x 2gh = mgh

Total energy at C

EC = Ep + Ek

EC = 0 + mgh
EC = mgh

Hence, energy at all points remains same.

Conservation of energy in a simple pendulum

Let us consider the example of an ideal simple pendulum (frictionless). We can see

that the mechanical energy of this system is a combination of its kinetic energy
and gravitational potential energy. As the pendulum swings back and forth, a

constant exchange between the kinetic energy and potential energy takes place.
When the bob attains its maximum height, the potential energy of the system is the

highest whereas the kinetic energy is zero. At the mean position, the kinetic energy