• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2
3. 3
3
4. 4
4
5. 5
5
6. 6
6
7. 7
7
8. 8
8
9. 9
9
10. 10
10
11. 11
11
12. 12
12

# Liquid Friction.

Extracts from this document...

Introduction

Nick Earnshaw

Bedford School

Candidate 3440

AS Coursework – Making Sense of Data

## Apparatus

Not in diagram:

• Stopwatch
• Top pan balance (accurate to nearest 0.1g)
• Micrometer screw gauge
• Several different size ball bearings.
• Small magnet
• Long ruler

## Method

The apparatus was setup as on the previous page, a ruler was used to mark the depths of 0.2m and 0.7m. The glycerol was left to settle.

The mass of each steel ball bearing was measured using a top pan balance and the diameter was measured using a micrometer screw gauge. The results from this were recorded and each measuring device was reset to zero each time.

Each steel ball bearing was coated in glycerol and then released from just below the surface of the glycerol, using tweezers.

The time taken for each steel ball bearing to drop from a depth of 0.2m and 0.7m was timed using a stopwatch and then recorded. This step was repeated a further two times for each steel ball bearing.

The steel ball bearings were retrieved after each attempt, using a small magnet.

## Results

I have formatted a table with the data attained from the experiment described above, each row of data relates to a different steel ball bearing.

The density of glycerol used was 1262 kg/m3.

 mass diameter time to fall 0.5m (g) (mm) (s) 1 2 3 Average low* 1.58 70.4 70.8 70.5 70.6 0.13 3.18 18.2 18.1 18.3 18.2 0.25 3.91 12.2 12.5 12.4 12.4 0.44 4.75 8.7 8.7 8.7 8.7 0.88 6.00 6.0 6.0 6.0 6.0 1.04 6.35 5.3 5.4 5.4 5.4 1.40 7.00 4.4 4.6 4.6 4.5 2.04 7.91 3.6 3.8 3.7 3.7 3.44 9.45 2.8 2.8 2.9 2.8

* This mass could not be accurately recorded using the top balance.

## Strategy and Approach

The above text is descriptive, it does not analyse the physics involved. My role within the investigation is to analyse results given to me. To effectively approach this target, I need to do some planning.

When the experiment was shown to me I took some notes, these are on a separate A4 lined sheet.

Middle

x

=

We can therefore equate this. This gives us the force in Newton’s.

Force (gravity) =

This allows us to make a statement, which then can be simplified.

Force (downwards) =  -

Force (downwards) =

The force acting downwards can also be expressed using stokes law.

- velocity of ball (at terminal velocity)

- coefficient of viscosity

Force (downwards) =

This is an expression for stokes law, and requires that the ball is travelling at its terminal velocity. We can use stokes law, and the equation for Force (downwards) found earlier to allow us to find the coefficient of viscosity of the liquid that the ball is moving through.

=

=

I used this approach to find the coefficient of friction of the liquid as shown in the table below.

Velocity was calculated by the equation below.

Speed =

 mass radius velocity b volume b density f viscosity (kg) (m) (ms-1) (m3) (kg/m3) η 4dp 1.61E-05 7.90E-04 7.09E-03 2.07E-09 7.82E+03 1.2586 1.30E-04 1.59E-03 2.75E-02 1.68E-08 7.72E+03 1.2955 2.50E-04 1.96E-03 4.04E-02 3.13E-08 7.99E+03 1.3858 4.40E-04 2.38E-03 5.75E-02 5.61E-08 7.84E+03 1.4074 8.80E-04 3.00E-03 8.33E-02 1.13E-07 7.78E+03 1.5346 1.04E-03 3.18E-03 9.32E-02 1.34E-07 7.76E+03 1.5318 1.40E-03 3.50E-03 1.10E-01 1.80E-07 7.79E+03 1.5816 2.04E-03 3.96E-03 1.35E-01 2.59E-07 7.87E+03 1.6678 3.44E-03 4.73E-03 1.76E-01 4.42E-07 7.78E+03 1.7988 Averages: 7.82E+03 * 1.4815

The coefficient of friction that the experiment data has produced seems reasonable, and follows a trend. As the radius of a sphere increase so does the coefficient of friction. This is a positive relationship. However, the coefficient of friction should be the same for all the different ball bearings used.

The actual frictional drag will increase with radius, but viscosity is a ratio between shearing stress and the velocity gradient, hence it should remain constant as long as other factors such as temperature are not changed.

There is a positive relationship between radius2 and velocity.

Conclusion

Human error

This is likely to contribute the biggest problem to reliability and accuracy to the investigation; calculations are based on data collected from a human.

Humans can only judge things to an accuracy of ±0.1s. The human reaction time coupled with the accuracy of the basic stop watched used could see a variation of almost ±0.2s.

This means that the velocity calculated based on the time it takes the ball to travel the 0.7m distance can be inaccurate because of the human error involved when using a stopwatch.

The problems of the stopwatch and the use of are probably the biggest factor sin causing uncertainties and inaccurate results.  But this did not prevent me from making suitable analysis.

## Temperature

Temperature can have a large effect on the viscosity of a fluid, since it gives the molecules more energy and the bonds will become weaker, meaning that the viscosity will be decreased. But the experiment was all done on the same day, in the same room so any change in temperature will be negligible.

## Improvements

To solve the problem of human error, a photodiode arrangement could be setup to electronically calculate the speed of the ball bearing. Also, a more instantaneous result could be attained if the distance was shorter, and closer to the bottom of the cylinder.

There are problems with the photodiode setup, and would require the ball bearing to be accurately dropped from a specific position.

An extension to the investigation could be the measurement of velocities at more than one intervals, perhaps every 0.1m, this would allow me to work out if the ball had reached terminal velocity or not.

Also, more care should be taken when releasing the ball bearing. The position from which the ball is dropped should be measured, and kept the same each repeat.

## End of Investigation

pages         type

17                 total

12                 normal

02                 graphs

03                data

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. ## EXPERIMENT TO DETERMINE THE VISCOSITY OF GLYCERINE.

All humans have a reaction time. This is the time taken between observation and reaction (in this case starting and stopping the stopwatch). The fact that there is variation between the repeated readings indicates that there is a measurement error of this nature.

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

This doesn't provide sufficient results because the change in viscosity between each temperature is small. In order to improve this in the final experiment I will use a 30 cm measuring cylinder. This would enable the sphere to travel further, so that the viscosity for different temperature will vary enabling me to see a trend between them.

1. ## An Investigation into the terminal velocity of steel ball bearings in Glycerol.

The ball now falls at a continuous speed. This is the maximum velocity (i.e. the terminal velocity). The forces are balanced, so this depicts Newton's first law of motion. Apparatus These are the required apparatus for the investigation, as shown in the diagram: � Large measuring cylinder � Steel ball bearings of various radii � Magnet (on a string)

2. ## Measuring the Viscosity of Honey

pen Magnet Balance Scale Method The set up of the apparatus should be designed to allow the terminal velocity of ball bearings to be determined accurately. The mass of the graduated cylinder should be measured using our balance. The measurement should be as exact as possible.

1. ## The Flywheel as an Alternative Energy Storage Device for Electric Vehicles (EV): Problems Associated ...

the stress is Now we have an equation that defines the stress that the rim of the flywheel experiences at a given radius, rotational speed, and density. The maximum tensile breaking stress that the flywheel can tolerate depends on the molecular properties of the material which it is built from.

2. ## This investigation is about what factors affect friction.

Therefore I have chosen the factor - WEIGHT. PREDICTION My prediction for this investigation is that; the more the weight of the object, the more force will be needed to move the object because when you put more weight it makes 2 surfaces grip together with more force.

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

Tape measure Stop clock Tray Bung Magnet Bunsen to heat oil (in a pan). Note: Each experiment shall be repeated 3 times and an average calculated to plot a graph. Method and Results tables Experiment 1 For the first experiment, I decided to measure the speed of a ball bearing descending through water.

2. ## Investigating the Relationship Between Temperature and Viscosity.

Drop the ball bearing into the honey tube. 5. Start the stopwatch when the ball bearing reaches the first timed distance mark, and stop the stopwatch when it reaches the second timed distance mark. 6. Repeat this three times for the same temperature to get reliability. 7. Heat the water around the honey by 10�c 8.

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