I understand why it needs to exist, otherwise the Earth wouldn’t keep spinning, coins would fall over immediately when you tried spinning them, artificial gravity wouldn’t be possible, etc. But I’m not sure how it works out physically. (nb. I’m talking without regard to drag, friction, etc. For example out in space where those are negligible factors.)
By definition, a spinning object is under acceleration (individual points on the object are constantly turning around the center of rotation, which is a form of acceleration in linear physics). And force requires energy, so why doesn’t the spinning of an object expend its angular momentum and slow it down over time?
Along the same vein, how does artificial gravity work in this context? As I understand it, centrifugal force is a fictitious force, but if I am inside a spinning object I am still being pressed against it as it turns and subjected to acceleration (from an observer’s point of view, at least). And so since I am being accelerated, something has to be using energy to accelerate me, right?
I apologize if I am sounding stupid but this has been wracking my brain for the last while and I’m desperate to figure out the answer. Thank you for any help!
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Force doesn’t “require” energy necessarily. A force perpendicular to the direction of motion does no work. If you want to be precise, work done is the integral of the dot product between the force vector and the infinitesimal change of position.
So if you push something in the direction it’s moving, you give it kinetic energy. If you push something against its motion, you take it’s kinetic energy. And, with a rotating object, when the force (the centripetal force) is perpendicular to the motion (the rotation), no work is done.
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