Answer: the average velocity decreases
Explanation:
From the provided data we have:
Vessel avg. diameter[mm] number
Aorta 25.0 1
Arteries 4.0 159
Arteioles 0.06 1.4*10^7
Capillaries 0.012 2.9*10^9
from the information, let be the mass flow rate,
is density, n number of vessels, and A is the cross-section area for each vessel
the flow rate is constant so it is equal for all vessels,
The average velocity is related to the flow rate by:
we clear the side where v is in:
area is π*R^2 where R is the average radius of the vessel (diameter/2)
we get:
you can directly see in the last equation that if we go from the aorta to the capillaries, the number of vessels is going to increase ( n will increase and R is going to decrease ) . From the table, R is significantly smaller in magnitude orders than n, therefore, it wont impact the results as much as n. On the other hand, n will change from 1 to 2.9 giga vessels which will dramatically reduce the average blood velocity