Question

The two spheres, one of which is hollow and other solid, have identical masses and moment of inertia about their respective diameters. The ratio of their radii is given by
(1) 5 : 7
(2) 3 : 5
(3) 3 : 5
(4) 3 : 7

Answer 1

Forth option iss correct

Answer 2

the moment of inertia of hollow sphere along diameter is = 2mr(1)^2/3[equation 1]
the moment of inertia of solid sphere along diameter is =2mr(2)^2/5 [equation 2]

Given that both the moment of inertia are equal. on equating equation 1 and 2, we get

r(1)^2/r(2)^2 = 3/5
hence r(1)/r(2) = √3/√5.