Q18 The bob of a pendulum is released from a horizontal position. If the length of the pendulum is 1.5 m, what is the speed with which the bob arrives at the lowermost point, given that it dissipated 5% of its initial energy against air resistance?
Consider the extreme position (horizintal) :-
The kinetic energy at this position is zero as velocity is zero.
Thus total energy is given by :
Now consider the mean position (lowermost point) :
Here the potential energy of bob is zero.
Whereas kinetic energy is :
Further, it is given that 5 per cent of energy is dissipated due to air resistance while coming down.
Thus energy equation becomes (conservation of energy):-
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