# An equilateral triangle ABC is cut from a thin solid sheet of wood, (see figure) D, E and F are the mid-points of its sides as shown and G is the center of the triangle. The moment of inertia of the triangle about an axis passing through G and perpendicular to the plane of the triangle is I0. It the smaller triangle DEF is removed from ABC, the moment of inertia of the remaining figure about the same axis is I. then : (a) I=I0 (b) I=I0 (c) I= (d) I=I0

## Question ID - 50298 :- An equilateral triangle ABC is cut from a thin solid sheet of wood, (see figure) D, E and F are the mid-points of its sides as shown and G is the center of the triangle. The moment of inertia of the triangle about an axis passing through G and perpendicular to the plane of the triangle is I0. It the smaller triangle DEF is removed from ABC, the moment of inertia of the remaining figure about the same axis is I. then : (a) I=I0 (b) I=I0 (c) I= (d) I=I0

3537

Answer Key : (d) -

Suppose M is mass and a is side of larger triangle, then  and  will be mass and side length of smaller triangle

=

So, I=I0=

Next Question :
 There are two long co-axial solenoids of same length l. the inner and outer coils have radii r1 and r2 and number of turns per unit length n1 and n2 respectively. The rate of mutual inductance to the self-inductance of the inner-coil is : (a) (b) (c) (d)