What is the Minimum Force Required to Inject into a Vein Using a Syringe?

[smillphysics]

A syringe with a plunger of diameter 2 cm is attached to a hypodermic needle with a diameter of 2.1 mm. What minimum force (in N) must be applied to the plunger to inject into a vein where the pressure is 16 torr above atmospheric pressure.


P=F/A since P will be constant throughout F/Aplunger= F/A vein

First 760torr=1 atm=1.01*10^5N/m^2, which gave me the pressure in the vein =2126.3. Then I said that P, which is 2126.3* area of the plunger (pi*r^2)
2126.3*pi*(.002)^2=.00668 which sound be by answer- the F. Although this is not correct. Where am I going wrong?

 

[LowlyPion]

Check too to see that you are using radius and not diameters.

Diameter of 2 cm means radius or 1 cm = .01 m.

 

[smillphysics]

Thanks- that was why I was incorrect.