From: SFPhysics@aol.com
Date: Sun Apr 15 2001 - 12:36:07 PDT
From: SFPhysics@aol.com Message-ID: <98.13620170.280b5227@aol.com> Date: Sun, 15 Apr 2001 15:36:07 EDT Subject: Baseball Distance Question
> Pinholers,esp you Physics teachers- I keep hearing
> Mike Krucoe (sp?) one of the baseball Giants
> announcers say that a batted ball traveled further
> because the pitcher threw it faster..so heres the
> question, or experiment: suppose you set up a T (like
> the little leaguers use) and set a baseball on it. You
> use a machine to hit the ball so its struck with the
> same force every time. Then you use a pitching machine
> and set it so it throws at the same velocity every
> time. Will the thrown ball,when hit by the bat, travel
> further than the ball struck from the T? thanks Dan
>>
Hi Dan:
Think about it for a moment. The ball bounces off the bat by first
compressing elastically then rebounding because of the stored elastic
potential energy. The bat need not even be moving for the ball to rebound.
What happens when a ball is thrown at a stationary object and rebounds if the
speed of the ball is increased? And, it will work with any ball that
exhibits elastic properties. Could you drop a ball from 1 metre and then
another at 2 metres to have it hit a bat that is laying on the ground? What
do you think will be the results? What would be the result if the bat were
moving upward at 1 m/s? Do what Einstein called mind experiments and you can
then confirm the hypothesis with simple tests. What confuses about the
baseball question is that the high speed of the baseball cannot be observed
easily.
This all should lead into the question of how the ball effects the speed of
the bat and the section on elastic collisions gets to be really fun. The bat
to ball mass ratios can be duplicated on an air track to show the students
what occurs. Taking a moment to think about momentum will open many more
questions.
One of my Physics devices was an old audiovisual reject record player that
would revolve at 78 rpm, 45 rpm, 33-1/3 rpm, and 16-1/6 rpm. To test a
hypothesis my students would tape a small toy plastic bat to the turntable.
An inclined plane would provide a toy ball at a speed dependent upon how high
up the plane it was started and could give each ball started at the same
point the same energy. The students would then play with the variables and
arrive at their hypothesis. Great fun!
Best wishes,
Al Sefl
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