And in physics and from fluid dynamics, we know that our volume flow rate of the blood queue is equal to the change in pressure between some .1 and some .2 inside our blood vessel divided by the resistance of that blood vessel. Now, if we take this equation and we plug it in for the resistance, we basically get the following equation. So Q is equal to pi radius, the power of four multiplied by the change in pressure divided by a multiplied by the viscosity multiplied by the length of that blood vessel. Now this equation influid dynamics is known as placier's equation. And as long as we assume that the blood is incompressible and that the fluid is flowing, the blood is flowing in laminar or streamlined flow, then we can use this equation to study and understand the way that our blood flows inside our blood vessels. Now, why is this equation important?