Great video. I have to wonder and ask, in your explanation of why we need to add the fictitious forces, you said that it is because the problem is at a uniformly rotating reference; what does that mean?
We use frames of reference (which are really cleverly chosen coordinate systems) to describe the observer who's watching the physics unfold in front of them. In this case, the camera is the observer. In the footage at 1:10, the camera no longer sees the disk spin because it's (effectively) spinning with it. So when the disk breaks into a bunch of fragments, we're now observing those trajectories from this "uniformly rotating frame of reference". Now that we're in this frame, we can't simply use Newton's 2nd Law anymore, that only works in an *inertial* frame of reference. At least, we can't use it unless we modify it by adding some *fictitious forces*. For a uniformly rotating frame, those are the Centrifgual and Coriolis Forces.
Of course General Relavity tells us that the inertial frame of reference is actually the free-falling one, and the force we call "gravity" is also just a "fictitious" one resulting from a non-inertial frame of reference. In practice we use non-inertial frames of reference all the time (far more often than inertial ones), and within such frames of reference these forces are just as real as any other.
Great video. I have to wonder and ask, in your explanation of why we need to add the fictitious forces, you said that it is because the problem is at a uniformly rotating reference; what does that mean?
We use frames of reference (which are really cleverly chosen coordinate systems) to describe the observer who's watching the physics unfold in front of them. In this case, the camera is the observer. In the footage at 1:10, the camera no longer sees the disk spin because it's (effectively) spinning with it. So when the disk breaks into a bunch of fragments, we're now observing those trajectories from this "uniformly rotating frame of reference". Now that we're in this frame, we can't simply use Newton's 2nd Law anymore, that only works in an *inertial* frame of reference. At least, we can't use it unless we modify it by adding some *fictitious forces*. For a uniformly rotating frame, those are the Centrifgual and Coriolis Forces.
@@madaydude_physics Thank you, I'll wonder more about it and hopefully be able to truly say, 'I understand it!'
Of course General Relavity tells us that the inertial frame of reference is actually the free-falling one, and the force we call "gravity" is also just a "fictitious" one resulting from a non-inertial frame of reference. In practice we use non-inertial frames of reference all the time (far more often than inertial ones), and within such frames of reference these forces are just as real as any other.