# Homework Help: How high should the bottle be placed above the needle?

1. Apr 11, 2010

### huybinhs

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

A patient is to be given a blood transfusion. The blood is to flow through a tube from a raised bottle to a needle inserted in the vein. The inside diameter of the 3.82 cm long needle is 0.393 mm and the required flow rate is 3.88 cm3 of blood per minute. How high should the bottle be placed above the needle? Obtain r and h from the Tables in the book. Assume the blood pressure is 19.3 torr above atmospheric pressure.

2. Relevant equations

Q = [pi*r4*$$\Delta$$P] / [8$$\eta$$*L]

3. The attempt at a solution

Q = [pi*r4*$$\Delta$$P] / [8$$\eta$$*L]

=> $$\Lambda$$P = [(3.88*10^-6)/60s) * 8*4*10^-3*3.82*0.01] / pi*(0.1965)^4 = 16877 Pa

h = (P2 - Patm + $$\Delta$$P ) / $$\rho$$ * g

= 2573 Pa - 101325Pa + 16877Pa / (1.05*10^3 * 9.8) = wrong answer.

2. Apr 12, 2010

### huybinhs

Any ideas?

3. Apr 13, 2010

Any one?