• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# EXPERIMENT TO DETERMINE THE VISCOSITY OF GLYCERINE.

Extracts from this document...

Introduction

Nneka Ezeigwe. Physics coursework.

EXPERIMENT TO DETERMINE THE VISCOSITY OF GLYCERINE.

## Procedure

A series of different sized ball bearings were dropped into a measuring beaker containing glycerine. The time taken to travel between two marks on the beaker was recorded. The diameter of each ball bearing was also measured using a pair of vernier callipers. Each experiment was repeated three times. The diagram and readings are shown below. TIME/S DIAMETER/MM T1 T2 T3 Taverage 1.00 82.08 78.81 76.95 79.28 1.50 37.07 36.42 35.53 36.34 2.00 21.20 20.77 20.17 20.71 3.17 8.45 8.18 7.99 8.21 4.00 5.18 5.24 4.99 5.14 4.76 3.74 3.73 3.64 3.70

Note that the average readings have been taken to reduce or eliminate any error present.

I will now plot a graph to make the relationship between the diameter of the ball bearings and the time taken to travel a distance of 162mm.

The graph shows that there is an inverse relationship between the time taken and the diameter of the steel ball. The curve has a decreasing negative slope.

When a steel ball (or any object for that matter) is dropped into a liquid, it experiences certain forces.  They are:

• The weight of the object acting downwards
• The upthrust acting upwards and t
• The Viscous drag F acting upwards. Every fluid has a property called viscosity. This is an internal property of the fluid that offers resistance to the movement of particles through it.

Middle

πηvr

Where η= the viscosity of the fluid.

From this formula, we can see that the viscous drag on the bigger ball is bigger than the viscous drag on the smaller ball. This is because the velocity increases as well as the radius. The weight downward also increases and the graph implies that this does so on a greater scale than the velocity and the radius. Hence, the time taken is less for a bigger ball bearing than for a smaller one.

The resultant force acting on the ball bearing is given by:

W-U-F

The ball bearing continues accelerating downwards until:

W-U-F=0.

At this point, the ball has attained a terminal velocity and is in a state of free fall.

Now, W=4/3πr3ρg

And   U=4/3πr3σg

Sir George Gabriel Stokes also gave the formula for finding terminal velocity. This is given by:

4/3πr3ρg – 4/3πr3σg – 6πηrvt =0

∴ vt = (2r2(ρ-σ)g) / 9η

This can be compared to the formula:

Y  =   M    x    +   C

Therefore, I will plot a graph of the terminal velocity against the radius squared (r2).

The gradient of this straight-line graph will be 2((ρ-σ) g) / 9η.

Where ρ is the density of the sphere, which is equal to 7930 kg/m3

and σ is the density of glycerine, which is equal to   1260 kg/m3

Conclusion

SOME CALCULATIONS TO BACK UP MY WORK.

HOW DID I DETERMINE THAT THE VELOCITY BETWEEN THE TWO RUBBER BANDS WAS EQUAL TO THE TERMINAL VELOCITY?

This can easily be proved with Stokes law. It states that:

vt = (2r2(ρ-σ)g) / 9η

Therefore η=(2r2(ρ-σ)g) / 9 vt

I then chose two random corresponding vales of vt and r2.

I chose the values r2= 2.5*10-7  vt  =2.04*10-3

And the values      r2= 40*10-7 vt  =31.25*10-3

Using the formula above, if indeed, the velocity I calculated is equal to the terminal velocity; I would obtain the same value for η in both cases.

Calculating gives me η=1.78012 pa for the first set and 1.8593 for the second set. Within the limits of experimental error, these are the same and so I can safely assume that the velocity between the two rubber bands is equal to the terminal velocity.

## CONCLUSION

This experiment was a successful one. The results obtained were within the limits of experimental error. Though errors occurred, this is unavoidable and they were detected and reduced to as bare a minimum as possible. The expected relationship between the velocity and the radius squared was obtained from the graph.

I can safely conclude that the viscosity of the glycerine used in the experiment is 1.8560775Pa within the limits of experimental error.

Page  of

This student written piece of work is one of many that can be found in our GCSE Forces and Motion section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related GCSE Forces and Motion essays

1. ## Bouncing Ball Experiment

This also proves the accuracy of the experiment. The results of the experiment were obtained with a method that ensured that every drop was under similar conditions which ensured a fair test. Therefore the results are valid. Improvements that could be made to the experiment if future work was to

2. ## The effect of the temperature on the viscosity of the syrup.

In order to eliminate this error in the final experiment, I will use a magnet so that the sphere will remain attracted to the it throughout the process of removing it. In order to do this I will be holding the magnet on the outside of the measuring cylinder.

1. ## Measuring the Viscosity of Honey

A Micrometer is a device which enables you to measure small thicknesses to a high degree of precision. The picture below shows its parts, to measure the diameter of a ball-bearing with a micrometer screw gauge, screw up the micrometer using its ratchet until its jaws are fully closed.

2. ## Practical investigation into Viscosity in liquids (Stokes Law).

0.23 0.227 50-70 0.22 0.22 0.22 0.220 Experiment 1.2 The second part of the first experiment measured the time taken for five differently sized ball bearings to descend through water. The purpose of this part of the experiment was to make it more clear how surface area and mass* affects the rate of descent.

1. ## Bouncing balls experiment.

Height bal dropped from (m) Height ball bounces (cm) For five test for each ball Average height of the bounce Tennis ball 56==>0.056 0.2 8 9 8 10 11 9.2 0.4 18 21 22 24 23 21.6 0.6 34 32 35 33 33 33.4 0.8 47 49 48 49 46 47.8 1.0 50 51 52 51 51 51 1.2

2. ## Investigation into the effect of temperature on viscosity

?v = 2 r� ?steel g -2 r� ?fluid g and cancel common factors 9 ?v= 2 r� (? steel - ?fluid)g divide by 9v ?= 2 r� (? steel - ?fluid) g substitute v for s/t (v=s/t) 9v ? = 2 r2 (? steel - ?fluid) g 9 (s/t)

1. ## Squash Ball and Temperature Investigation

reliable, are: * Force used to Drop Ball According to how much force is applied to drop the ball, it will bounce higher or less.

2. ## Bouncing balls.

h(mean) h(max) h(min) 2 1.1 1.1 1.11 1.09 1.12 1.104 1.12 1.09 1.8 1 1.01 1.01 1.02 1.03 1.014 1.03 1 1.6 0.91 0.91 0.9 0.9 0.89 0.902 0.91 0.89 1.4 0.79 0.77 0.78 0.78 0.78 0.78 0.79 0.77 1.2 0.68 0.7 0.68 0.67 0.69 0.684 0.7 0.67 1 • Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to 