STOP HOME EXPLORE CONTENT ORDER THE POSTER SET POST FEEDBACK ALL UPDATES
WHEN STARS GO BOOM! OVER THE RAINBOW HOW TALL IS TALL? CHOKE UP ON THAT BAT! THAT'S FAST!
Bat
Push to moverotateplayersTry it


Push to move WHY DO WE NEED TO PUSH THINGS
TO GET THEM TO MOVE?


Things don't start moving by themselves. If something is at rest, you have to push it to get it going. For a push of a given size, some objects will move more easily than others. Inertia is a measure of how much something resists being put into motion. Mass is a measure of inertia. The more massive an object is, the harder you have to push to get it moving.

rotate WHAT ABOUT MAKING SOMETHING ROTATE?

To get something to rotate, a twisting force has to be used. But it is more than just the mass that determines how hard it is to rotate something. It also matters how far that mass is from the point around which you are trying to rotate. If most of the mass is close to the center of rotation, it is easier to make it rotate. For example, a disk will roll more easily than a ring with the same mass and size.

BASEBALL PLAYERS ARE SCIENTISTS?

players
"I'm sure that of all of the home runs I hit, at least half of them came when I was choking up slightly."
Ted Williams
When the pitcher is bringing the heat, Megan gets a jump on the ball by choking up on her bat.

Well, some might be. But almost all of them know that it is harder to get good “bat speed” with a big, heavy bat. When a pitcher is throwing the ball at 100 miles per hour, the batter has less then a second to hit the ball, so getting the bat around fast matters! If a batter wants to be able to swing a bat more quickly, they choke up on the bat. This puts the heaviest part of the bat a little closer to where they are twisting the bat with their wrists.

The next time you play baseball, do an experiment. Take your favorite bat and try choking up on the grip a little. You’ll find that you can swing a little faster, and that’s a good thing! Tell your coach


"IT'S ALL ABOUT ROTATIONAL INERTIA!"


TRY IT!

Try it

ROTATIONAL INERTIA (Example: Twirling a baseball bat.) Hold a bat horizontally in your hand, gripping it in the middle. Twist it back and forth to rotate it, like in the figure above. Now grip that same bat all the way at the end and try to rotate it again. It is much harder. That’s because the mass is farther away from the rotation axis.

bottom
Back







FaceBookTwitterYouTubeFlickr