Final answer:
The force per unit area exerted by blood against the walls of a blood vessel is called blood pressure. To calculate the net force in a given section of artery, one needs to multiply the pressure difference by the cross-sectional area of the artery. The power expended maintaining the flow is found by multiplying this net force by the average blood speed.
Step-by-step explanation:
The force per unit area that blood places on the inside wall of a blood vessel is known as blood pressure. In physics, this concept can be further explained by looking at the blood hydrostatic pressure, which is the force blood exerts against the walls of a blood vessel or heart chamber. When considering blood flow, Poiseuille's law comes into play, and blood flow is regulated by changes in vessel size and blood pressure. Blood vessels are not rigid but elastic, and adjustments to blood flow are primarily made by varying the size of the vessels, as resistance is so sensitive to the vessel radius.
Considering the specific scenario where the pressure drop along a length of artery is 100 Pa, the radius is 10 mm, and the flow is laminar with an average speed of the blood of 15 mm/s, we can calculate the net force on the blood by using the pressure and cross-sectional area of the artery (A = πr^2). Since the pressure drop (P) is 100 Pa and the radius (r) is 10 mm or 0.01 m, the area (A) is π * (0.01 m)^2. The net force (F) is then the product of the pressure and the area (F = PA).
To find the power expended maintaining the flow, we multiply the net force by the average speed of the blood flow (power = force × speed). This requires consistent units, so ensure the speed of blood is also converted to meters per second if it isn’t already. Moreover, the circulation system intricacies, such as how each larger vessel branching into smaller vessels affects the total cross-sectional area, thus impacting blood pressure and resistance, are essential factors in understanding how the cardiovascular system maintains blood flow and pressure throughout the body.