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A disc of radius 0.4 meter and mass $1 \mathrm{~kg}$ rotates about an axis passing through its center and perpendicular to its plane. The angular acceleration is $10 \mathrm{rad} \mathrm{s}^{-2}$. The tangential force applied to the rim of the disc is
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$2 \mathrm{~N}$
$\mathrm{R}=0.4 \mathrm{~m}, \mathrm{M}=1 \mathrm{~kg}, \alpha=10 \mathrm{rad} / \mathrm{s}^2$
$\mathrm{I}=\frac{\mathrm{MR}^2}{2}=\frac{1 \times(0.4)^2}{2}=0.08 \mathrm{~kg} \mathrm{~m}^2$
Torque, $\tau=\mathrm{I} \alpha=0.08 \times 10=0.8 \mathrm{~N}-\mathrm{m}$
Also, $\tau=$ FR
or $F=\frac{\tau}{R}=\frac{0.8}{0.4}=2 \mathrm{~N}$
$\mathrm{I}=\frac{\mathrm{MR}^2}{2}=\frac{1 \times(0.4)^2}{2}=0.08 \mathrm{~kg} \mathrm{~m}^2$
Torque, $\tau=\mathrm{I} \alpha=0.08 \times 10=0.8 \mathrm{~N}-\mathrm{m}$
Also, $\tau=$ FR
or $F=\frac{\tau}{R}=\frac{0.8}{0.4}=2 \mathrm{~N}$
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