A gymnast can really carry out each of these sorts of rotation on the similar time—that’s what makes the game so attention-grabbing to observe. In physics, we might name this sort of motion a “inflexible physique rotation.” But, clearly, people aren’t inflexible, so the arithmetic to explain rotations like this may be fairly difficult. For the sake of brevity, let’s restrict our dialogue simply to flips.
There are three varieties of flips. There is a structure, during which the gymnast retains their physique in a straight place. There is a pike, during which they bend at a few 90-degree angle on the hips. Finally, there’s a tuck, with the knees pulled up in direction of the chest.
What’s the distinction, in phrases of physics?
Rotations and the Moment of Inertia
If you wish to perceive the physics of a rotation, you must think about the second of inertia. I do know that’s a strange-sounding time period. Let’s begin with an instance involving boats. (Yes, boats.)
Suppose you’re standing on a dock subsequent to a small boat that’s simply floating there, and isn’t tied up. If you place your foot onto the boat and push it, what occurs? Yes, the boat strikes away—however it does one thing else. The boat additionally quickens because it strikes away. This change in pace is an acceleration.
Now think about that you simply transfer alongside the dock and choose a a lot bigger boat, like a yacht. If you place your foot on it and push it, utilizing the identical pressure for a similar quantity of time as you probably did for the smaller boat, does it transfer? Yes, it does. However, it doesn’t improve in pace as a lot because the smaller boat as a result of it has a bigger mass.
The key property on this instance is the boat’s mass. With extra mass, it’s tougher to alter an object’s movement. Sometimes we name this property of objects the inertia (which isn’t to be confused with the second of inertia—we’ll get to that quickly).
When you push on the boat, we are able to describe this force-motion interplay with a type of Newton’s Second Law. It seems to be like this:
Illustration: Rhett Allain
