Briefing session Monday 2 Feb Overview This is a lab course and the purpose is twofold i t is a complement to the fluid mechanics you learn in MT24A Atmospheric and Ocean Dynamics it gives you experience in laboratory measurement practice data analysis techniques and report writing ID: 462783
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Slide1
MT25F Atmospheric Analogues
Briefing session
Monday
2
FebSlide2
Overview
This is a lab course, and the purpose is twofold:
i
t is a complement to the fluid mechanics you learn in MT24A Atmospheric and Ocean Dynamicsit gives you experience in laboratory measurement practice, data analysis techniques and report writingModule Convenor is Chris Westbrook (me!)email c.d.westbrook@reading.ac.ukmy office is room 502 in Philip Lyle building
Demonstrators are Hannah Parker and
Lenka
Novakova
Lab Technicians are Ian Read and Catherine SnellSlide3
manualSlide4
Some things we are looking for
Intelligent data and
e
rror analysis when using your measurements to test theoryExample:Imagine an experiment where you have a slope and a small ball, mass , at the top of the slope. You let go of the ball and measure the velocity
of the ball when it gets to the bottom of the slope. You make a measurement for several different heights of slope Theory tells you that
So plot
vs
(not
vs ), because you know that theory tells you this plot should be a straight line, with slope of
Need to estimate error in
and
– see manual for manipulating error estimates
Plot error bars on both axes (where appropriate)
Estimate slope of straight line – you can see more than 1 line could be consistent with these large error bars so need to estimate the maximum and minimum possible slope
Compare to theoretical value of
– consistent?
Slide5
What if errors are very big?
Consider the case where the error on a single measurement of the quantity
is very big, but random (rather than systematic). We can improve this situation by repeating the measurement several times and taking the mean (average)
The error in the mean of
estimates is less than the error in each of them individually – the manual discusses how to calculate this “standard error”
The error is reduced by a factor of approximately
by averaging
1 measurement of
for each value of
:
Average 8 measurements of
for each value of
:
Slide6
What if my data don’t match theory?
This does not necessarily mean you did the experiment wrong!
Is there a systematic discrepancy , even when you take into account the error bars, then you need to mention it, and discuss possible reasons why. – e.g. in our example we might find that the ball rolled 20% slower than theory
Think about reasons why this might be different to theory. What are we assuming in the theory which might be a poor assumption?
Or is there a measurement problem not accounted for in our error analysis? What might this be?
Red = theory
Blue = measurementsSlide7
What’s in an abstract?
What is it?
A very short summary of what you did and the main results/conclusions
It should stand alone from the rest of you work. In other words, you can’t assume that the person that reads the abstract has read the rest of the lab report.
Why is it useful?Every article in a scientific journal has an abstractEvery time you go to a scientific conference you have to write an abstract (and usually the abstract determines whether you get to give a talk or not)Your final year dissertation will require you to write an abstract
In general short concise summaries that convey the maximum scientific meaning are something that most research scientists need to produce on a regular basis – and you only get good at it by practicing.Slide8
What’s in an abstract?
- an example from one of my papers
PURPOSE / SPECIFIC QUESTIONS TO ANSWERSlide9
What’s in an abstract?
- an example from one of my papers
MAIN RESULT, INCLUDING RELEVANT QUANTITATIVE INFORMATIONSlide10
What’s in an abstract?
- an example from one of my papers
ANALYSIS OF WHAT RESULT MEANS AND CONCLUSIONSlide11
What I expect you to know already
How to plot a graph with labels, units, and error bars
The material you are covering in MT24A
Basic maths and physics [manipulation of equations, differentiation, simple geometry, relationship between frequency and period; wavelength and wavenumber; etc]How to experiment systematically [change one parameter at a time, think about what quantities to measure, etc]
If you don’t feel confident about these things, please come talk to meSlide12
See you next Monday afternoon!
Any questions?Slide13
What’s in an abstract?
- an example from one of my papers
PURPOSE / SPECIFIC QUESTIONS TO ANSWER
MAIN RESULT, INCLUDING RELEVANT QUANTITATIVE INFORMATION
ANALYSIS OF WHAT RESULT MEANS AND CONCLUSION