# 5 kg steel ball and 9 m cord of negligible mass make up a simple pendulum that can pivot without friction about the point O.

**A 4.5 kg steel ball and 9 m cord of negligible mass make up a simple pendulum that can pivot without friction about the point O. This pendulum is released from rest in a horizontal position and when the ball is at its lowest point it strikes a 4.5 kg block sitting at rest on a shelf. Assume that the collision is perfectly elastic and take the coefficient of friction between the block and shelf to be 0.64. The acceleration of gravity is 9.81 m/s 2. What is the velocity of the block just after impact?**