Energy changes at B K.E. = O
at highest pt. vel. = O
P.E. = mgh
∴ the bob is at height h
K.E. + P.E. = O + mgh = mgh …(i)
At A: As the bob moves towards A from B its height goes on decreasing and h at A is zero, but its vol. goes on increasing.
∴ At A, P.E. = 0 and K.E. = mgh
∴ P.E. + K.E. = 0 + mgh = mgh ….(ii)
At C : As the bob continues to move forward from B to C, its velocity = 0 but height increases to h
∴ At C K.E. = 0 and P.E. = mgh
∴ K.E..+ P.E. = 0 + mgh = mgh …(iii)
Thus we find that sum total of K.E. and P.E remains constant which is in accordance with conservation of energy.
