Question for the Day 27-9-2007

1. A solid sphere of mass M, radius R and having moment of inertia about an axis passing through the centre of mass as I, is recast into a disc of thickness t, whose moment of inertia about an axis passing through its edge and perpendicular to its plane remains I. Then, radius of the disc will be


(A) 2R/SQRT(15)


(B) R*SQRT(2/15)


(C) 4R/SQRT(15)

(D) R/4

2. CuSO-4 decolourises on addition of KCN, the product is


(A) Cu(CN)-4 (B) [Cu(CN)-3
(C) Cu(CN)-2 (D) CuCN

3. Given an isosceles triangle, whose one angle is 120° and radius of its incircle = SQRT(3) . Then the area of the triangle in sq.units is

(A) 7 + 12*SQRT(3) (B) 12 − 7*SQRT( 3)

(C) 12 + 7*SQRT( 3) (D) 4π