Physics Question

[pilumnus]

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What is the volume flow rate through an artery with blood moving at 0.20m/s in a diameter of 1.0E-2?

AAMC said to multiply the blood speed by the cross-sectional area (which would be a circle for an artery I assume)

However, they set it up like this:
V = (0.20)x(pi/4)(1e-2)^2

Why is it pi/4? why not just pi? area of a circle is pi(r)^2 right?

Sorry if this is a stupid question...

 

[mmcoffee]

I think it's the same. Try doing it your way (using the numbers and pi r squared), you'll see that if you simplify you get the same thing. Sorry I've never explained concepts before I hope that makes some sense

 

[Cawolf]

You are given diameter, so they use the formula that A = (pi/4)*d^2 which is the same as A = (pi)r^2

d = 2r so d^2 = 4r^2