Calculate Average Blood Speed with Volume Flow Rate | Physics Problem Help

AI Thread Summary
The discussion focuses on calculating average blood speed using the volume flow rate in an artery. The volume flow rate is given as 3.5E-6 m^3/s, and the radius of the artery is 5.4E-3 m, leading to an average blood speed of 0.0382 m/s for part (a). For part (b), the constriction reduces the radius by a factor of 7, meaning the new radius should be 5.4E-3 m divided by 7, not subtracted from the original radius. The correct average blood speed at the constriction is calculated using this new radius, which is essential for accurate results. Understanding the correct interpretation of the radius reduction is crucial for solving the problem accurately.
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Volume Flow Rate, Help?

1. The problem statement, all variable and given/known data

The volume flow rate in an artery supplying the brain is 3.5E-6 m^3/s.

(a.) If the radius of the artery is 5.4E-3 m, determine the average blood speed.
(b.) Find the average blood speed at a constriction in the artery if the constriction reduces the radius by a factor of 7. Assume that the volume flow rate is the same as in part (a.)

Homework Equations



Q = Volume flow rate = AV

The Attempt at a Solution



I got (a.) but I need help with (b.). I think my radius for part (b.) is wrong, but I don't know how else to get it.

For part (a.) I got 0.0382 m/s by using

Q = Volume flow rate = AV = pi x r^2 x v = 3.5E-6 m^3/s

and using the given radius in part (a.) I solved for v.

For part (b.) I divided the given radius by 7, and subtracted that from the original radius to get a radius of 4.63E-3, and I put it into the equation the same way as part (a.) and I got 0.0520 m/s, but it's wrong. Help?
 
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They mean that the constricted radius is 1/7 of the original radius, not 6/7 of it.
 
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