JEE Main On 8 April 2017 Question 17
Question: Moment of inertia of an equilateral triangular lamina ABC, about the axis passing through its centre and perpendicular to its plane is I0 as shown in the figure. A cavithy DEF is cut out from the lamina, where D,E,F are the mid points of the sides. Moment of inertia of the remaining part of lamina about the same axis is [JEE Online 08-04-2017]
Options:
A) $ \frac{15}{16}I _0 $
B) $ \frac{3I _0}{4} $
C) $ \frac{7}{8}I _0 $
D) $ \frac{31I _0}{32} $
Show Answer
Answer:
Correct Answer: A
Solution:
- $ I _0=kml^{2} $ $ BC=l $ $ I _{DEF}=K\frac{m}{4}{{( \frac{l}{2} )}^{2}} $ $ =\frac{k}{16}ml^{2} $ $ I _{DEF}=\frac{I _0}{16} $ $ I _{remain}=I _0=\frac{I _0}{16} $ $ =\frac{15I _0}{16} $
