Hold the Mayo COROI\\'ARY arteries are responsible for supplying oxy- genated blood to heart muscle. Coronary heat dis- ease is caused by the arteriosclerosis (the deposition of plaque along the arterial walls) of those arteries. One common response of the body to coronary arteriosclero- sis is to increase the blood pressure. An average nor- mal blood pressure is 120 mm Hg maximum (systolic) when the heart is pumping its hardest, falling to 80 mm Hg when the heart is relaxed (diastolic) between beats.! This is typically reported as \"120/80 mm Hg.\" (Read: \"120 over 80.\") If your systolic pressure gets above 140 mm Hg, you will be diagnosed with incipient high blood pressure. Pressures at that level and above can cause damage to the body's organs. Lets see what physics can tell us about coronary arteriosclerosis and its con- sequences. NORMAL ARTERY BLOGD FLOW Figure 1: Source: Midland Cardiovascular Ser- vices, NZ In a \"mild\" case of coronary arteriosclerosis, plaque may line the walls so that it occludes 1/3 of the cross section of the artery. One might predict at first glance that the flow rate in the occluded artery is 2/3 of the healthy artery. Let's see how accurate that is. 1. The radius of a typical open artery is 1.5 mm. What is the radius of an artery that is 33% occluded? (i.e. 33% of the cross-sectional area is taken up by plaque.) 2. According to the H-P equation, by what fraction does the artery resistance increase? 3. Assuming that the pressure drop across the artery remains the same, calculate the ratio of current flow (@) in the 33% occluded vs. the open artery. 4. The body attempts to compensate with reduced flow in part by increasing the blood pressure. How much would the pressure drop across the artery (AP) have to increase in the 33% occluded artery to have the volume of blood flow (@) equal to that in the open artery? 5. Assuming you have completely open arteries now, estimate what your own systolic pressure would have to be in order to compensate for the decreased flow