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obog t1_j0gnqyo wrote

Reply to comment by TheSmartestBanana in Does rotation break relativity? by starfyredragon

The centrifugal force isn't real, it's only an observed force when you're inside the rotating frame of reference. A constant force does still have to be applied, it's just often an internal force, not an external one. In the case of an object rotating in space, there is a force of tension acting in the outer parts of the object pulling them back towards the center. Due to that the object will stay in rotation without any outside force, but the key term there is outside. there still has to be some force to keep an object rotating, it can just be an internal force. That internal force (as I said, the force of tension for an object rotating) is the centripetal force.

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TheSmartestBanana t1_j0gqq4u wrote

Centripetal force can only be felt by a point inside the rotating body as well. That point obviously has an acceleration because the directional component of its velocity is changing constantly. The rotating object as a whole is not accelerating and therefore requires no net force. There are a lot of forces that hold an object together, but those forces do no cause an acceleration on that object and therefore cause no force to act on the object itself as a whole.

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atmsk90 t1_j0hgbik wrote

I think there is some confusion between static and dynamic equilibrium here. Centrifugal "force" is simply inertia. It's much easier to visualize by considering a point mass on a massless arm. The arm has to exert a force on the mass not as a result of any applied force from somewhere else, but just as a result of needing to accelerate the mass toward the center of rotation.

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hydroxypcp t1_j0kuo20 wrote

for this question you do have to look at individual particles of the rotating body though. If we take a human body as the rotating body, then the eyes are accelerating and thus not an inertial frame of reference

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