# Homework Help: Calculating viscosity

1. Sep 10, 2007

### physics_forums

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

A shearing force of 100 dynes is applied to the side of a rectangular plate of 5 x 10 cm dimensions placed on top of a 0.5 mm high column of Newtonian fluid that is initially at rest. As a result of the shearing force, the plate moves at a speed of 11.2 cm/sec. What is the viscosity of this Newtonian fluid? (5 pts)
PS: Can you guess what this fluid is?

2. Relevant equations

Viscosity = (Force/Area)/(Velocity/Length)

3. The attempt at a solution

Force = 100 dynes
Area= 50 cm^2
Velocity= 11.2 cm/sec
Length= .05 cm

Viscosity = (100/50)/(11.2/.05)
=(2)/(224)
=.00893 Poise
=.0000983 CeniPoise

Can someone double check my work and see if Im on the right track? Im positive I have the right inputs and the right equation, but I have a feeling Im messing up on the units because the answer seems way too low. Thanks in advance!

2. Sep 10, 2007

### nicktacik

I think you moved your decimal place the wrong way when you converted to cP.

3. Sep 10, 2007

### physics_forums

Yes, yes I did. So then the viscosity would be .893, so would that make the Newtonian fluid be water? Water is at 1 Centipose and thats the closest thing to my answer. Thanks for the look out Nick