There is also an amazing amount of physics involved in the batball collision, and in the performance
and behavior of the bat itself.
The ball experiences a significant amount of deformation during the collision, much more so
than the bat. By comparing the two movies we can also see that the amount of deformation is
noticeably larger for the faster incoming ball speed.
The speed of the ball is considerably less after the collision than it was before the collision.
The impact between bat and ball is an extremely violent one, in which the bat imparts a huge
force on the ball thereby causing it to change directions and gain speed. Consider a baseball
weighing 5.125oz (mass = 0.145kg) which approaches the bat at a speed of 90mph (40.2m/s).
After the collision with the bat, with a contact time of 0.7milliseconds (0.0007s)
[1,2]
the bat has a
speed of 110mph (49.1m/s) in the opposite direction. Using Newton's second law we can
estimate the average force acting on the ball during the hit:
Plugging in the numbers we find the average force to be
F
avg
=18,436 N, which is equivalent to
4124 lbs of force. The impulse delivered by this force is the product of the average force the the
contact
The force that the bat exerts on the ball is not a constant during the entire duration of contact, but
instead follows more of a sinesquared time history, starting and ending at zero and peaking
approximately half way through the duration of contact. The figure at left illustrates this. The area under a
forcevstime curve is the implulse provided by the force. The average force, calculated above, is the
constant force which acts for the same duration as the actual force, and encloses the same area under its
forcevstime curve (providing the same impulse) as does the actual force. Data for forcevstime curves
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 Spring '10
 Grant
 pH, Force, Mass, Momentum, Home run, Babe Ruth

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