cross posting to sci.engr.mech. (Been too long since I've done this)
Hi,
>
> 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)/95
> 5 = ((2gr2)(d1-d2)/V) / 9
>
> Where:
>
> V = velocity of fall (cm sec-9),
> 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
> 5 = viscosity of medium (dyne sec cm-2).
>
> 5 = ((2gr2)(d1-d2)/V) / 9
>
> 5 = ((2*980*0.82)(7.62-1.26) / 23) / 9
>
> 5 = 38.54 Dynes
> 5 [DATA]: 0.942 N sm-2
>
> im not great at physics, but something looks very wrong with
> that value 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*5*r*v
> &
> mg - u = 6*pi*5*r*v
>
> I have no idea if the above equation work is correct? It seems
> the other two take account of viscous drag? Weight & upthrust,
> should i not be taking these into account when calculating
> viscosity?
>
> 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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