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# Baseball Bats Part 2

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Today we were hitting in the field house as part of our practice and I decided to focus on something I always knew happened, but never knew why.  Every time a baseball bat rolls, it always does so in a circular fashion.  This can be really annoying especially when it gets set down and then all of the sudden it starts randomly rolling off in a circle and depending on speed, always goes in a different path.  The more I thought about it, the more I was amazed that it could be explained simply with physics.  The bat is essentially a long rod with two ends of different diameters, and therefore, circumferences.  Because there is no part of a bat that allows the top and bottom to rotate independently, the two different ends must rotate at the exact same angular velocity.  But because they are different sizes, one rotation of one end will cover more ground than the single rotation of the other end.  For an example, think of a bat with one end of the bat with a circumference of 5 cm and the other end with a circumference of 2 cm.  If the whole bat is rolled along the ground so the ends spin at 1 revolution per second, that means the top of the bat is covering 5 cm every second, and the bottom is covering 2 cm every second.  This change in distance traveled forces the bat to rotate lengthwise to accommodate for the difference because as we said before, neither end can speed up or slow down to even out the displacement of the unequal ends.  Through a little physics, I was able to explain something that every baseball player has thought about at least once.  And now I get to explain it to everyone on my team and watch them pretend like they care (even though this is really some cool stuff.)

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