# Calculating blood pressure increase with Poiseuille's equation

1. Sep 18, 2014

### FenderFan54

1. The problem statement, all variables and given/known data
Hello! I don't usually ask for help on homework, but I am really stuck and my physics teacher has no clue what she is doing. She doesn't really understand the material. Here is the question: There are two carotid arteries that feed blood to the brain, one on each side of the neck and head. One patient's carotid arteries are each 11.2 cm long and have an inside diameter of 5.1mm . Near the middle of the left artery, however, is a 2.0-cm-long stenosis, a section of the artery with a smaller diameter of 3.2mm. For the same blood flow rate, what is the ratio of the pressure drop along the patient's left carotid artery to the drop along his right artery?

2. Relevant equations
Poiseuille's equation: Q=pi(r^4)Δp/(8ηL)

Given Value of blood flow rate, Q=8.3x10^-5 m^3/s (by same they mean the one stated earlier in the text)

3. The attempt at a solution
I tried to simply plug and chug the values but did not get the answer right. I got about 1.5 for the ratio. I know this because the homework must be submitted online. Any help would really be appreciated!

2. Sep 18, 2014

### Staff: Mentor

Can you show what you've tried? How did you set up the calculations?