<prompt> If diameter of a vessel is increased double -Blood flow increases four foldBlood flow decreases four foldBlood flow increases sixteen-foldBlood flow decreases sixteen-fold  <response>: Ans. is c i.e., Blood flow increases sixteen-fold Poiseuilles Law Hagen-Poiseilles law o The Poiseuilles equation states that: -Where Q is the rate of flow. Pl - P2 is the pressure difference across the vessel provided P1 P2, n is the viscocity of blood, r is the radius and L the length of the tubeo If everything else remains constant, blood flow is directly poroportional to 4th power of radiuso Thus, if the diameter or radius is increased to to double, blood flow will increase 16 times. 