A gymnast can truly carry out each of all these rotation on the similar time—that’s what makes the game so attention-grabbing to look at. In physics, we’d name this kind of motion a “inflexible physique rotation.” However, 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 sorts of flips. There’s a structure, through which the gymnast retains their physique in a straight place. There’s a pike, through which they bend at a couple of 90-degree angle on the hips. Lastly, there’s a tuck, with the knees pulled up in direction of the chest.
What’s the distinction, by way of physics?
Rotations and the Second of Inertia
If you wish to perceive the physics of a rotation, you’ll want to take into account the second of inertia. I do know that’s a strange-sounding time period. Let’s begin with an instance involving boats. (Sure, boats.)
Suppose you’re standing on a dock subsequent to a small boat that’s simply floating there, and isn’t tied up. In case you put your foot onto the boat and push it, what occurs? Sure, the boat strikes away—however it does one thing else. The boat additionally hastens because it strikes away. This alteration in velocity is an acceleration.
Now think about that you simply transfer alongside the dock and choose a a lot bigger boat, like a yacht. In case you put your foot on it and push it, utilizing the identical drive for a similar period of time as you probably did for the smaller boat, does it transfer? Sure, it does. Nevertheless, it doesn’t improve in velocity as a lot because the smaller boat as a result of it has a bigger mass.
The important thing property on this instance is the boat’s mass. With extra mass, it’s tougher to vary an object’s movement. Generally 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).
Whenever you push on the boat, we are able to describe this force-motion interplay with a type of Newton’s Second Legislation. It seems like this:
Illustration: Rhett Allain