question_answer

In the triangular sheet shown, \[PQ=QR=l,\]If m is the mass of the sheet, its moment of inertia about PR is

A)  \[\frac{m{{l}^{2}}}{24}\]                         

B)  \[\frac{m{{l}^{2}}}{12}\]

C)  \[\frac{m{{l}^{2}}}{6}\]               

D)  \[\frac{m{{l}^{2}}}{18}\]

Correct Answer: B

Solution :

As, \[{{l}_{PR}}={{l}_{QS}}=\frac{m{{l}^{2}}}{12}\]  (for the figure) Hence, only for triangular part, moment of inertia \[I=\frac{m{{l}^{2}}}{12},\] where m is the mass of the triangular sheet.