# Homework Help: Human Pressure Help Please!

1. Mar 29, 2005

### jmandas

I'm having a difficult time getting this blood pressure problem to work out. Here is the question:
Neglecting the pressure drop due to resistance, calculate the blood pressure in mmHg in an artery in the brain 30 cm above the heart. The pressure at the heartis 120mmHg and the density of blood is 1.05g/cm^3.
The answer in the book is 96.8mmHG but I keep getting a long negative answer!
Here is the formula I'm using:
Pressure in head=Pressure in heart - Height from heart to brain(density of blood)(9.8m/s^2).(may be using wrong formula)

Any help would be great I don't know what else to do?!

2. Mar 29, 2005

### dextercioby

The formula u're using is correct.I'm sure that u're screwing up the units.It would be okay to use SI-MKgs units.U'll need

$$\rho_{Hg}^{1 \ atm,293K}\sim13.595 Kg m^{-3}$$

Daniel.

3. Mar 29, 2005

### dextercioby

Yes,i know that,on normal basis,the blood's temperature is not 20°,but ~37°,but using the density of Hg which i gave u,u get the answer ~96.73 mmHg...

Daniel.