Question

Two steel balls of mass 25 g and 75g are attached by strings to a peg P and released from a horizontal position. After the collision between the steel balls, the 25g ball is observed to rebound to its original position. A) what position does the 75g ball first come to rest after the collision? B) How much mechanical energy is lost in the collision? Each ball is 0.25m away from the peg.

Answer 1

Since both the balls fall down by length 0.25 m ( length of the string) , they will have the same velocity before the collision.(but opposite directions obviously)

And if the 25g ball is again rebounding to the same height ====> that the energy has been conserved.Also, it needs the same velocity as of before collision to rebound to the same height.

Hence even after the collision, both balls rebound with the same speed and reach to their positions.

And no energy is lost in these collisions.