A pendulum of length 2m released at P. When it reaches Q, it losses 10% of its total energy due to air resistance. The velocity at Q is

If v is velocity of pendulum at Q and 10% energy is lost while moving from P to Q Hence, by applying conservation of between P and Q12mv2=0.9 (mgh)⇒v2=2×0.9×10×2⇒v=6 m/sec