Question

A hypodermic needle is 1.5 cm long and has an inner radius of 0.016cm. What excess pressure is required along the needle so that the flow rate of water though it is 0.0013 kg/s? Use ç = 1.0 x 10-3 Ns/m2 for water.

the answet i have found is deltaP=758017 Pa

using the formula ...

delta P = R ( delta V/delta t)

Answer 1

This looks like a laminar pipe flow problem. I do not recognize your � symbol, nor the units Ns/m2. Is that the viscosity?

The friction factor is 64/(Reynolds number). You can either use pipe flow formulas with that friction factor, or special formulas for Poiseuille flow, which you can find at
http://galileo.phys.virginia.edu/classes/311/notes/fluids2/node6.html

Answer 2

75807pa