Three particles, each of mass `m` grams situated at the vertices of an equilateral triangle `AbC` of side `I` cm (as shown in the figure). The moment of inertia of the system about a line `AX` perpendicular to `AB` and in the plane of `ABC`, in gram-cm^2 units will be.
.

Options

A. `2ml^(2)`
B. `(5)/(4)ml^(2)`
C. `(3)/(2)ml^(2)`
D. `(3)/(4)ml^(2)`

Answer

B

Explanation

`I_(AX)=mx^(2)+m(0)+m(l^(2))`
`x=lsin30^(@)=l//2`
`I_(AX)=m((l)/(2))^(2)+m(l)^(2)`
`=(5)/(4)ml^(2)`