# Homework Help: Volume and pressure

1. Apr 11, 2007

### cyberdx16

1. The problem statement, all variables and given/known data
When physicians diagnose arterial blockages, they quote the reduction in flow rate. If the flow rate in an artery has been reduced to 30% of its normal value due to plaque formation, and the average pressure difference has increased by 30%, by what factor has the plaque reduced the radius of the artery?

2. Relevant equations

Poiseuille's Law.

3. The attempt at a solution

what i used was R=(.7/1.3)^.25 and get that only 85.6% of the radius of the artery is available, and has been reduced by 14.4%

2. Apr 11, 2007

### denverdoc

I think you want to use .3 in the numerator, ie

flow is now 30 percent of original, not been reduced by 30%

Last edited: Apr 11, 2007
3. Apr 11, 2007

### cyberdx16

wouldn't the presure rate be increased by .3 so from its original, which is 1 and add .3 for the increase. But yeah i just tried .3 and it didnt work

4. Apr 11, 2007

### denverdoc

Its both .3 and 1.3, (.3/1.3)^.25 is that what you tried?

5. Apr 11, 2007

### cyberdx16

yeah you are right denverdoc! thx

6. Apr 11, 2007

### denverdoc

NP. FYI when occlusion reaches 80 percent and above, bad news. This guy has lost some exercise tolerance but still in decent shape re meeting oxygen demands.