- #1
tntcoder
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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)/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 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 don't know the Forces involved?
Thanks very much for any help, and sorry if I've made a load of mistakes.
Jack
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 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 don't know the Forces involved?
Thanks very much for any help, and sorry if I've made a load of mistakes.
Jack
Last edited: