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# Rotational Mechanics question

A disc of mass m and radius R is attached to a rectangular plate of the same mass breadth and length 2R . Find moment of inertia of this system about diameter of of disc.

Note by Zahid Shekh Mohammed
4 years, 3 months ago

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please specify how it is attached as it would be of great help in solving the problem... · 4 years, 3 months ago

the disc and rectangular are attached about their ends · 4 years, 3 months ago

Hey you have mentioned that it is a $$\underline{rectangular}$$ $$\underline{plate}$$ of same mass, breadth and length 2R which actually contradicts that it is a rectangle. I have solved the problem taking it to be a square.

Here is how I got it: $$\I_{of disc about diameter}$$=$$\frac {1}{4}$$M$$R^{2}$$ and $$\I_{of square about diameter of plate}$$= $$\frac {4}{3}$$M$$R^{2}$$ . So $$\I_{required}$$=$$\frac {19}{12}$$M$$R^{2}$$ · 4 years, 3 months ago

Is it attached about its length or width ? · 4 years, 3 months ago

about length · 4 years, 3 months ago

Hey dear, please post complete question because incomplete ques. causes undesired anxiety. You have not mentioned about which diameter ? Please post the complete ques. once more. · 4 years, 3 months ago

Can I email the photo of question please give your email · 4 years, 3 months ago

but answer is 31MRsqaure\12 · 4 years, 3 months ago

No actually breadth is R and length is 2R · 4 years, 3 months ago