Question

why integral y dash equal to zero in parallel axis theorem

Answer 1

The parallel axis theorem, also known as Huygens–Steiner theorem, or just as Steiner's theorem,named after Christiaan Huygensand Jakob Steiner, can be used to determine the mass moment of inertia or the second moment of area of a rigid body about any axis, given the body's moment of inertia about a parallel axis through the object's center of gravity and the perpendicular distancebetween the axes.