• 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.  

image00.png

Readings

        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.

image01.png

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.

...read more.

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

...read more.

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

...read more.

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

See related essaysSee related essays

Related GCSE Forces and Motion essays

  1. The effect of the temperature on the viscosity of the syrup.

    It was inappropriate for me to use 1 litre beaker since it only allowed the sphere to travel for 10cm. The syrup was very lowly viscous at temperatures of 600, 700 and 800 and so the sphere traveled with a very high velocity.

  2. Bouncing Ball Experiment

    Height the ball was dropped from (cm) (h1) Average of the middle three repeats (cm) (h2) 0.7 � h1 (cm) 0.7 � h1 - Average of the middle three repeats (cm) 200 105 140 35 190 103 133 30 180 102 126 24 170 99 119 20 160 95 112

  1. Investigation into the effect of temperature on viscosity

    steel - ?fluid) g 9 (s/t) Fair test: There are many variables that may affect this investigation, all have been considered thoroughly and precautions will be taken to ensure that the experiment runs as smoothly as possible. The viscosity is the one of the most important variables of the investigation.

  2. 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.

  1. Squash Ball and Temperature Investigation

    allow a nice, neat bounce whereas other surfaces will alter the bounce due to indentation in the surface and bumps etc. To make the test fair, all testing will be done on a bench surface throughout the experimenting procedure. * Angle of Surface The angle of the surface at which

  2. Bouncing balls experiment.

    Information on gravitational potential energy, kinetic energy, velocity, and elasticity will be from preliminary work done in physics in previous years during secondary school as well as from boos and sources from the internet. Results table Type of ball Mass (g==>kg) Height bal dropped from (m) Height ball bounces (cm)

  1. Practical Investigation Into Viscosity

    Stokes papers on the motion of incompressible fluids, the friction of fluids in motion, and the equilibrium and motion of elastic solids exemplifies his wide range of influence in physics.

  2. Investigating the viscosity of liquids.

    will push the object upwards until it is only partially immersed and displaces exactly its own weight of fluid. On the other hand, if the upthrust on the fully immersed object is less than the object's weight, then there is a net downward force and consequently the object sinks.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work