Angular velocity and period of a disc rotating about point on circumference

AI Thread Summary
The discussion centers on finding the angular velocity and period of a solid disc rotating about a point on its circumference. Participants express confusion over the problem's wording, particularly the distinction between "circumference" and "surface." Clarification reveals that the disc indeed pivots around a point on its circumference, despite the initial ambiguity. The moment of inertia provided is I = (mR^2)/2, and a small angle approximation is suggested. Overall, the conversation highlights the challenges in interpreting the problem statement and the need for precise definitions in physics problems.
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Homework Statement



Find the angular velocity and period of oscillation of a solid disc of mass m and radius R about a point on it’s surface.

Homework Equations



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The Attempt at a Solution



This is really giving me trouble because it seems like a SHO problem mixed with a rotational motion problem, and I don't even know where to start. Any help would be greatly appreciated :confused: .
 
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Is that all you are given, exactly the way the problem is stated? That's exactly like "find the velocity of an object moving in a straight line"! An object can move with almost any velocity and can rotate with almost any angular velocity. Oh, and in your title you say "rotating about point on circumference" but your problem says "about a point on it’s surface". Those are not at all the same thing. Which is correct?
 
HallsofIvy said:
Is that all you are given, exactly the way the problem is stated? That's exactly like "find the velocity of an object moving in a straight line"! An object can move with almost any velocity and can rotate with almost any angular velocity. Oh, and in your title you say "rotating about point on circumference" but your problem says "about a point on it’s surface". Those are not at all the same thing. Which is correct?

Yes, the disc pivots around a point on its circumference, according the very unhelpful diagram my professor gave me. She's also Sri Lankan so her English isn't great, which would explain the "surface" part. And the question is a direct quote, that's all I have. :confused: ^ 100000

EDIT: sorry, she also gave us: "I = (mR^2)/2, Assume sin(theta)≈theta"
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
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