Centrifugal force is classified as a fictitious force that arises in non-inertial (rotating) frames of reference, while centripetal force is a real force that acts inward on an object moving in a circular path. The discussion highlights that centrifugal force does not have an actor exerting it, making it an artifact of perception rather than a true force. In contrast, centripetal force is exemplified by tangible forces such as tension in a string or friction from a road. The relationship between gravity and inertia is also explored, referencing Einstein's theories and the concept of inertial forces.
PREREQUISITESPhysics students, educators, and anyone interested in understanding the dynamics of forces in rotating systems and their implications in both classical and modern physics.
The centrifugal also acts on such objects. Its value is mω²r, so it is only equal to 0 for r=0.YellowTaxi said:- but it does not exist on objects that are moving with an angular rotation about the centre axis with an equal and opposite rotation to that of the frame. (because such objects are in fact not rotating and not moving at all).
well you could say they DO have a centrifugal force acting on them, but it's of magnitude zero.
DaleSpam said:I would say that the centrifugal force does exist in the rotating reference frame.
DaleSpam said:The centrifugal also acts on such objects. Its value is mω²r, so it is only equal to 0 for r=0.
I think you are thinking about the Coriolis force, which is -2m(ωxv). So it does depend on the velocity in the rotating reference frame.YellowTaxi said:No,
If you move with an ω numerically equal to the ω of the rotating frame but in the opposite direction, you aren't moving at all. And then mrω² for all values of r is zero. Even though from the rotating frame you seem to have an angular speed ω, you in reality are standing still.
That's why I think the rules for statics will work fine on a rotating frame , but anything moves at all [in any direction] and it all gets bizarre, and Newton flies out the window.
DaleSpam said:I think you are thinking about the Coriolis force, which is -2m(ωxv). So it does depend on the velocity in the rotating reference frame.
yes , that was exactly my point in my previous post. This object which appears to have circular motion when viewed from the rotating frame will in fact be standing perfectly still in space. The tension in the string (say), or the force from a retaining wall required to hold it there will be zero.If an object is stationary in the inertial reference frame then it obviously travels in a circular motion in the rotating reference frame.
You aren't moving with respect to the inertial frame.YellowTaxi said:No,
If you move with an ω numerically equal to the ω of the rotating frame but in the opposite direction, you aren't moving at all.
No. The ω in the formula for centrifugal force is due to the rotation of the frame; it's not the ω with respect to the rotating frame.And then mrω² for all values of r is zero.
Again, you are at rest with respect to the inertial frame, not the rotating frame.Even though from the rotating frame you seem to have an angular speed ω, you in reality are standing still.
To be used from a rotating frame, Newton's laws, including their application to statics, must be modified to include all relevant "fictitious" forces.That's why I think the rules for statics will work fine on a rotating frame , but anything moves at all [in any direction] and it all gets bizarre, and Newton flies out the window.
You're not talking about coriolis, but you should be. If you are moving with respect to the rotating frame, coriolis force must be considered.YellowTaxi said:no I'm not talking about coriolis at all here. We were both discussing mω²r which is not the coriolis force ;-)
It's certainly true that an object at rest in an inertial frame requires no net force to remain at rest. But if you choose to analyze the situation from the view of the rotating frame, it is certainly moving. Both centrifugal and coriolis forces are at work.yes , that was exactly my point in my previous post. This object which appears to have circular motion when viewed from the rotating frame will in fact be standing perfectly still in space. The tension in the string (say), or the force from a retaining wall required to hold it there will be zero.