Liquids with a high viscosity flow slowly (like golden syrup), whereas liquids which have lower viscosities flow faster (like water). There are many ways to measure viscosity. However I chose to do so by using a chrome ball bearing as this was the only sphere shaped object available to be used in the lab.
Stokes Law was derived by George Gabriel Stokes in 1851. This describes the drag force which is exerted on a sphere in a Newtonian fluid. The frictional force is measured in Newton’s which is experienced by the ball bearing as a result of the fluid being made to flow around it.
Where:
is the dynamic viscosity of the fluid in
R is the radius of the ball in m
V is the velocity of the ball in ms
To carry out our experiment we used:
- 900ML Sainsbury’s Golden Syrup
- 1 Litre Measuring cylinder
- Chrome steel ball bearing
- Manual stop watch
- Hard drive magnet
In my experiment I measured 900ml of Golden Syrup in a measuring cylinder. After this I measured my ball bearing with a pair of venire callipers I measured the ball bearing as it would help me with equations later on. I coated my bearing in golden syrup before dropping it in as this would reduce friction as the ball hit the golden syrup.
These are the results I gathered from my dropping.
Averages:
‘Medium’ – 21.686s
‘Small’ – 29.673s
There is an increase in speed as the ball’s radius gets bigger.
152MM Distance travelled
Speed of Balls:
Medium – 0.007 m/s
Small – 0.0051 m/s
The graphs show the ball bearing size the drop attempt and the time taken. The black line shows the average of the drops.
The medium sized ball has a small gradient on the graph, this could be because of air bubbles in the golden syrup during the test, this would create a small amount of extra time to get to the bottom as the air bubbles will create resistance.
The ball bearing weight can be determined with =mg
g=9.81
m=
p=Density in kg/m
The density of chrome steel is 0.283 lbs/cubic inch
()
This is in cubic inches but I need it in kg/m
The density in kg/m is 7833.4.13kg/m
V= Volume of sphere
R= Radius of sphere (0.00596m)
V = 0.0008868
M = 0.006947kg
Fg= 0.0682 – ‘Medium’ Ball
