If the kinetic energy of each ball is equal to that of the other,
then
(1/2) (mass of ppb) (speed of ppb)² = (1/2) (mass of gb) (speed of gb)²
Multiply each side by 2:
(mass of ppb) (speed of ppb)² = (mass of gb) (speed of gb)²
Divide each side by (mass of gb) and by (speed of ppb)² :
(mass of ppb)/(mass of gb) = (speed of gb)²/(speed of ppb)²
Take square root of each side:
√ (ratio of their masses) = ( 1 / ratio of their speeds)²
By trying to do this perfectly rigorously and elegantly, I'm also
using up a lot of space and guaranteeing that nobody will be
able to follow what I have written. Let's just come in from the
cold, and say it the clear, easy way:
If their kinetic energies are equal, then the product of each
mass and its speed² must be the same number.
If one ball has less mass than the other one, then the speed²
of the lighter one must be greater than the speed² of the heavier
one, in order to keep the products equal.
The pingpong ball is moving faster than the golf ball.
The directions of their motions are irrelevant.
