Question:
A square plate of mass $120 \mathrm{~g}$ and edge $5.0 \mathrm{~cm}$ rotates about one of the edges. If it has a uniform angular acceleration of $0.2 \mathrm{rad} / S^{2}$, what torque acts on the plate?
Solution:
Squeeze rod along axis $A^{\prime \prime}$ so it will behave as rod
$I=\frac{m a^{2}}{3}$
$\tau=I \alpha$
$=\frac{(0.120)(0.05)^{2}}{3}(0.2)$
$\tau=2 \times 10^{-5} \mathrm{~N}-\mathrm{m}$