# Problem on moment of inertia

Find moment of inertia of a uniform quarter disc of radius R
and mass M about an axis through its centre of mass and
perpendicular to its plane ........

I tried in the following way:

I considered the relation. I= Icm + Md2
Where d is the distance between required axis and centre of mass.......

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SteamKing
Staff Emeritus
Homework Helper
Find moment of inertia of a uniform quarter disc of radius R
and mass M about an axis through its centre of mass and
perpendicular to its plane ........

I tried in the following way:

I considered the relation. I= Icm + Md2
Where d is the distance between required axis and centre of mass.......
There's nothing wrong with your formula. However, it does require the use of the quantity (Icm) you are asked to determine by the original problem.

Do you know the center of mass location for a quarter circle?

In this problem, you must not only determine in location of the c.o.m. (if it is not already known) and also the moment of inertia of a quarter circle. I think it will probably take a little calculus to do both.

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K thanx for ur suggestion i will try to solve the problem

haruspex
Homework Helper
Gold Member
There's nothing wrong with your formula. However, it does require the use of the quantity (Icm) you are asked to determine by the original problem.
No, in this case i think the formula can be applied in the opposite direction usefully. It is relatively easy to find the M of I about the circle's centre (i.e. the corner of the quarter circle). Once the centre of mass has been determined, the M of I about that can be deduced from the formula.

SteamKing
Staff Emeritus
Homework Helper
It's not clear why the OP got the wrong answer as he posted no calculations. We don't know if he was using I about the origin, the c.o.m., or what.

In this case, Brevity is the enemy of Clarity, those two Irishmen who are eternal rivals.

haruspex