Question

This question considers blood pressure in living creatures. The following values for blood may be useful:

viscosity = 3 x 10-3 Pa s density = 1060 kg/m3.

(a) A bug sucks blood from other creatures through a small tube, 2 x 10-4 m long and with a radius of 5 x 10-6 m. The observed flow rate is 3.3 x 10-10 m3/s. How much pressure difference must the bug create to achieve this? (1.5 marks)

(b) When I’m upright, my head is about 0.3 m above my heart. What difference, if any, would you expect between the blood pressure in my head and where it’s usually measured - in my arm at the level of my heart?

(c) Reptiles generally have much lower blood pressure than humans. Tree-living snakes, however, have higher blood pressure than other reptiles, and their hearts are closer to their heads than for other snakes.
Discuss these observations in relation to the physics of fluids.

Answer 1