Transcript Bonn International School IB Diploma Physics

International School of Amsterdam
IB Diploma Physics
Investigating the Investigation
Now that you have some experience with
practical investigations, it is time to review the
requirements, in order to ensure that you are
working towards fulfilling all the criteria as well
as possible.
We will work through a typical investigation!
A Typical Investigation
Scenario
Any teacher knows that the smallest things can be a distraction to
students and the most innocent objects can be misused. An
example is the simple rubber band. Rather than being used to bind
bundles of loose objects together, their elastic properties are
liable to be used to turn them into projectiles.
Task
Your task is to investigate a factor of your
own choosing that affects the flight of a
rubber band.
Design - The Aim
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The aim must be a focussed problem or
research question
It cannot be simply a restatement of the
general task that has been provided
The task may, however, specify the
dependent variable
In this case it does not!
The Dependent Variable
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“The flight of a rubber band” is a
very general description
There are several characteristics of
“flight” that are readily measurable
and could become our dependent
variable
e.g. Range, flight time, or maximum
height
The Independent Variable
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Consider what variables you could
investigate. In this case, some
possibilities are:
 Amount of Stretch
 Angle of Launch
 The rubber band, e.g. length, thickness
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Choose one to investigate, bearing in
mind that once you finally reach a
conclusion, you will have to try and
explain it using basic principles.
The Controlled Variables
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All the possible independent variables
will be among the controlled variables
for the investigation
Other factors that might influence
the results must also be controlled
Possibility of Wind
Launch height
Are bounces allowed?
The Apparatus and Materials
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List all the apparatus and materials
you will use in your investigation
You may need to revise this list when
you have completed your plan for the
method
Be specific, especially with the ranges
of meters
The Method
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Give enough detail so that someone
else could follow it and end up doing
exactly the same as you would
Scientific texts use an impersonal,
passive style. (“The rubber band will be
stretched back to the 10 cm mark on the ruler…”)
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Write in the future tense. Anything else
is a give-away that you have written a report
afterwards, not a plan beforehand.
Controlling the Variables
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Describe how to set up the apparatus,
and adjustments you need to make
You may include a diagram
Explain how it is used in the
experiment
Make sure you refer to the
independent, controlled and dependent
variables in this stage
Collecting Sufficient Data
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Indicate any measurements that will be
made once at the start and recorded
individually
For the independent variable, give the
starting value, size of step, the final
value and how many repeats. (e.g. beginning
with an angle of 0 degrees from horizontal and increasing in
steps of 10 degrees up to a maximum of 80 degrees, firing 5
times at each angle.)
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Give details of how to make the
measurements, especially the dependent
variable.
Data Collection
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First record any one-off data
Draw up a result table for most of
the results
Headings with units and uncertainties at
the top
Independent variable in the first column
Dependent variable second
You may include columns for processed
data
Uncertainties
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Remember that all measured quantities
have a degree of uncertainty
You need to allow for the uncertainty that
arises in making the measurement and the
uncertainty inherent in the quantity itself
– In this case, you may be able to measure the
range of a flight to the nearest 0.01 m
– However, repeated flights may land up to 0.1 m
apart
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Give 1 s.f. in the uncertainty and the same
d.p. in the measurement.
Data Processing
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Data may be processed
mathematically, graphically or both
Errors and uncertainties must be
taken into account for the
assessment of aspect 3 of DCP
Clear presentation is required, making
your working easy to follow
With graphs, show where and how the
gradient has been calculated
Calculations
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Show individual calculations in full
Show sample calculations if you have
used a spreadsheet or made repeated
calculations
Show details of your error analysis (an
example will do if there are repeated
similar calculations)
Drawing Graphs
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Generally line graphs are required
Dependent variable on the vertical axis
Independent variable on the horizontal axis
Draw line of best fit or a smooth curve
Show error bars, or note if they are too
small to show
Include max. and min. error lines
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The requirements are the same for
computer-assisted graphing
Conclusion
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State any numerical conclusion clearly,
with uncertainty
Compare your answer with an expected
value or literature value. (Does that value lie
within the range of your uncertainty? - It should!)
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Describe any relationship using the
terms “direct”, “inverse”, or
“proportional” and explain how the graph
shows this.
You must also try and justify your
conclusion (using basic principles or explaining the
logic of your deduction)
Evaluating the Method
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Refer to any difficulties that arose
Note which measurements
contributed most to the uncertainty
in your answer
Focus on these when suggesting
improvements to the method
You are being asked for evaluation
not reflection. So, keep it impersonal. Do not
refer to learning from the experience or working
well with your partner.