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Im doing an experiment to determine the viscosity of glycerol this is my collected data:

Data:

Sphere radius: 0.8 cm

Sphere mass: 16.3 g

Sphere voume: 2.14 cm -³

Sphere density: 7.62 g cm -³

Glycerol density 1.26 g cm -³

Sphere Terminal Velocity: 23 cm/s

Light Gate Seperation: 20cm

Given value for viscoisty of glycerol in data book: 9420 10^-4 N sm-2

My Calculations:

By Stokes law:

V = (2gr²)(d1-d2)/9µ

µ = ((2gr²)(d1-d2)/V) / 9

Where:

V = velocity of fall (cm sec-¹),

g = acceleration of gravity (cm sec-²),

r = "equivalent" radius of particle (cm),

dl = density of particle (g cm -³),

d2 = density of medium (g cm-³), and

µ = viscosity of medium (dyne sec cm-²).

µ = ((2gr²)(d1-d2)/V) / 9

µ = ((2*980*0.8²)(7.62-1.26) / 23) / 9

µ = 38.54 Dynes

µ [DATA]: 0.942 N sm-2

im not great at physics, but something looks very wrong with that value :surprised cany anyone put me right, are my calculations correct and i have very in accurate data? Or have i used the wrong equation?

Ive seen lots of equations like:

F= 6*pi*µ*r*v

&

mg - u = 6*pi*µ*r*v

I have no idea if the above equation is correct? It seems the other two take account of viscous drag? Weight & upthrust, should i not be taking these into account?

And how can i use the above equations if i dont know the Forces involved?

Thanks very much for any help, and sorry if ive made a load of mistakes.

Jack

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# Futher Viscosity Help

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