ホームランの科学／The Science Behind Home Runs

DENJIRO: Today's topic is home runs in baseball. Take a look at this experiment we performed outside. You can see that the ball flew far, just like a home run. The speed of the bat is called the bat speed, and the speed of the ball is called the exit speed. Let's measure their speeds in the studio here. The exit speed was faster than the bat speed. If you throw a ball with a sling, the ball travels at the same speed as the sling. So why is it that in baseball, the exit speed is faster than the bat speed? Let me explain using these two metal balls. I'm going to strike the small ball against the big ball. The ball bounces back a lot, so the small ball's speed when it travels toward the big ball is almost the same as when it comes back. Now, let me strike the big ball against the small ball. The small ball was repelled at a speed faster than the big ball. If we compare this to tee hitting, the big ball represents the bat and the small ball the baseball. The small ball is repelled at the same speed as the big ball. In this case, since the big ball isn't losing any speed, the small ball moves at about twice the speed. The same thing happens with tee hitting, and that's why the exit speed is faster than the bat speed. Now, let me pull back both balls and have them strike each other. The small ball was repelled at an even faster speed. This is because both balls were moving. This is the same as when a batter hits a ball thrown by a pitcher. In baseball, the exit speed is faster than the bat speed because a heavy bat is used to strike a light ball. I hope energy will bring you all happiness. Our magic word is "Happy Energy!"