On this day of numerical glory, get to know pi in an unusual way: using the elastic collision of two different masses and a wall.

• The relation between velocity of approach and the velocity of separation for perfectly elastic collision, this approach is used to solve numerical like: a) How much the energy will be ...

If this is a perfectly elastic collision such that the total kinetic energy is constant, then this y-momentum must have the same magnitude as before the collision (but in the opposite direction).