Example, if you are holding an object in your hand that is spinning and you move your arm in a certain direction the object will feel heavier and in the opposite direction it will feel lighter. I assume it’s related to or caused by centrifugal force but have never heard a name for it.
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A spinning object has *angular momentum*, where it wants to keep spinning in the same direction. You can move it normally in any direction, but *rotating it* becomes very strange.
You see, momentum is a property of matter that describes its movement. A softball flying through the air has momentum, a stationary softball does not. Note that an object may have different momentums depending on your perspective, though that’s not important for this discussion.
For an example, a perfectly frictionless car on a flat road. You push gently on it for ten seconds, and it starts to slide forward slowly. You can go to the other side and push gently on it for ten seconds to stop it, or you could push harder for less time and also stop it.
This is because pushing harder changes its momentum faster.
*Angular* momentum is the same thing but for spinning objects. A spinning wheel takes force (or, more accurately, torque, the rotational version of force) and time to bring it to a halt. A faster and/or heavier wheel requires more force and/or time to get it started and stopped.
Momentum is conserved, though. If you took a clock and turned it around, it would spin the opposite direction, right? This means its momentum must have become the opposite of what it was before. I just said momentum is conserved – it cannot disappear – so something else must now have some spin in the original direction.
If you’re holding a spinning wheel and attempt to rotate it, you will feel that momentum from the wheel trying to spin you back. It will also resist turning, and try to turn itself at a different angle than the force you’re applying.
Hopefully my high school physics is up to par. Inertia is the word you’re looking for. An object in motion tends to remain in motion unless acted on by an outside force. In this case the outside force is your hand moving.
Mmn, you are looking at gyroscopes and gyroscopic precession.
The thing to keep in mind is that a spinning object wants to keep spinning along the same axis because of angular momentum. If you hold the thing at any point that isn’t in line with the center of gravity that creates torque. And if that torque isn’t adding to or subtracting to the spinning it is trying to change the direction of the axis it’s spinning on. And in a very counterintuitive way that will force the direction of the applied torque to change direction.
As for why it feels heavier or lighter think of holding a broom stick. If you are holding it vertically it’s not too bad. But if you point it forward now you have to support the weight of the stick which hasn’t increased, and keep it from rotating and it feels harder to hold.
Now think of holding a spinning bicycle wheel from only one side of the axle (if you haven’t done this maybe look up some videos). It’s the exact opposite. If you let the wheel precess sideways you only have to support the weight of the wheel, and don’t have to spare any strength keeping it upright. The wheel keeps itself vertical with the tradeoff that it now rotates around horizontally. If you try and force the thing to stop rotating horizontally you then have to resist that torque. Just instead of up and down the force is left to right.
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