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Question
Three particles, each of mass 200 g, are kept at the corners of an equilateral triangle of side 10 cm. Find the moment of inertial of the system about an axis passing through one of the particles and perpendicular to the plane of the particles.
Solution
let the axis of rotation passes through A and is perpendicular to the plane of triangle.
Therefore, we have
Net moment of inertia,
\[l = m r^2 + m r^2 \]
\[ = 2 m r^2 \]
\[ = 2 \times 200 \times {10}^2 \]
\[ = 400 \times 100\]
\[ = 40000 gm - {cm}^2 \]
\[ = 4 \times {10}^{- 3} kg - m^2\]
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