Re: In a bat and ball collision, is momentum conserved, why or why not?

Calculated momentum conservation assumes that the collision between bat and
ball is perfectly elastic, that is, that no energy is dissipated in friction or 
deformation of either the bat or the ball.

In the real world, that is not so. Slow-motion films of a ball-bat collision in
a typical baseball game show significant inelasticity: the ball deforms, the
bat (and ball) absorb some of the collision energy as frictional heating, and
so on. This means that, if you take real-world measurements of momentum 
transfer in a ball-bat collision, you will observe significant deviations from
the calculations (which assume perfect elasticity).

Remember that an "elastic" collision is one in which the colliding objects
DON'T deform; billiard balls, for example, undergo near-perfect elastic 
collisions in which momentum is transferred in its entirety. Notice that when
a cue ball strikes another ball dead-on, the cue ball stops. Its momentum has
been entirely transferred to the other ball.

                                              Dan Berger
                                              MadSci Administrator