Stephen Steadman, age 11, of Rochester, N.Y., for his question:

Why does a stick bounce?

Hold up a stick and let go. It starts to travel at once    pulled down, down towards the very center of the earth. We are used to this everyday event of falling objects and it does not surprise us. When the stick reaches the ground it stops it can go no further. If the stick fell upon a hard road, it may then turn around and travel in the opposite direction    up again. This might well surprise us if we weren't so used to seeing things bounce.

The reason why things bounce is very strange and very complex. It concerns the force of gravity, the force, or energy within falling bodies and the molecules of which substances are made.

Whether you notice or not, you use energy to lift up a sticks energy against the downward pull of gravitation. So long as you hold up the stick it has that much usable, or potential, energy. When you let go it starts to use that energy at once. If you toss it dawn rather than let it drop, you add that much more force, or energy, to the falling stick. Down it falls, dropping faster and faster, It gathers momentum, more speed and force as it goes. This moving force is called kinetic energy. This kinetic energy, plus the weight of the stick, is behind the smack with which it strikes the ground.

Then for a fraction of time, the stick is still. All the kinetic energy has gone into the smack, and the stick is left with only its own weight. A split second photo would show that the stick, plus its force, had made a dent in the hard ground    a dent which the weight of the stick alone is unable to hold.

In that split second, the ground gets ready to react and strike backs The molecules of which the ground is made react to straighten out that dent. The ground uses the force given it by the falling stick to recoil and spring back into its original position. In doing  this, it deals the fallen stick a counter blow and sends it bouncing back in its tracks.

Some substances make better bouncers than others. The molecules in other substances are lazy about springing back into their original positions. Stesl and ivory are very quick to right their wrongs and spring back with great force and great speed. These are the elastic, or resilient substances.

Baseballs and bats, as everyone knows, are made of resilient substances. Add this natural bounce to a traveling baseball, plus  the force behind pitcher Carl Erskine's good pitching arm and the force behind Carl Furillo’s good batting swing and we can expect our quota of home runs to round out the season.