Consider two uniform discs of the same thickness and different radii R1
= R and
R2
= $\alpha$R made of
the same material. If the ratio of their moments of inertia I1
and I2
, respectively, about their axes
is I1
: I2
= 1 : 16 then the value of $\alpha$ is :
Solution
Moment of inertia of disc, $$I = {{M{R^2}} \over 2} = {{\left[ {p\left( {\pi {R^2}} \right)t} \right]{R^2}} \over 2}$$<br><br>$I = K{R^4}$<br><br>${{{I_1}} \over {{I_2}}} = {\left( {{{{R_1}} \over {{R_2}}}} \right)^4}$<br><br>$${1 \over {16}} = {\left( {{R \over {\alpha R}}} \right)^4} \Rightarrow \alpha = {\left( {16} \right)^{{1 \over 4}}} = 2$$
About this question
Subject: Physics · Chapter: Rotational Motion · Topic: Centre of Mass
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