1. Take a long thread say 50-60 cm long.
2. Attach a small heavy object like a metal ball at one end.
3. Tie other end to a nail fixed to the wall as shown in figure.
4. Now pull the bob of the pendulum to one side to the position A1 and release it.
5. The bob swings towards opposite side and reaches the point A2 . It repeats the motion over and over again.
6. The potential energy of the bob is minimum at A and reaches maximum at A1 because the height of the bob is maximum at that position.
7. When the bob is released from this point (A1), its P.E. decreases and K.E. starts increasing slowly.
8. When the bob reaches the position A, its K.E. reaches maximum, and P.E. becomes minimum.
9. As the bob proceeds from A to A2 , its P.E. increases slowly and becomes maximum at A2 .
10. The total P.E. and K.E. at any point on the path of motion during the oscillation of the pendulum.
11. Thus the total mechanical energy in the system of pendulum remains constant.
