Question

With reference to Fig. 7.6 of a cube of edge a and mass m, state whether the following are true or false. (O is the centre of the cube.)

(a) The moment of inertia of cube about z-axis is I_z = I_x + I_y

(b) The moment of inertia of cube about z′ is I'_z = I_z + (m a²)/2

(c) The moment of inertia of cube about z'' is = I_z + (m a²)/2

(d) I_x = I_y

Answer 1

(a) False, perpendicular axis theorem is applicable only to a lamina.

(b) True

(c) False, z and z” are not parallel axes.

(d) True.