9702 Physics Practical Exam – Paper 32
 Question 1 – “Accurate experiment”: collect data & plot a graph
Set up the apparatus shown in the question paper.
Record length/mass etc of a given variable – always take at least 2 readings and use the
average of both as the answer. Plot these recordings in a table for e.g.
L1
L2
<L>
4.50
4.52
4.51
Do NOT forget to indicate units in final answer.
For angles measured with a protractor, record to the nearest degree e.g., 67°
For the table always take 6 sets of readings which use the whole range available
Do NOT forget the headings and units on the table for each quantity.
If a ruler with a mm scale is used, then measurements can be taken as for e.g., 4.5, 5.7,
6.5 etc.
Graph should be plotted so that at least half the grid is occupied in both x and y
directions.
Axes must be labelled with the quantity and corresponding unit.
If an anomalous point is present in the graph, it must be identified with a circle for e.g.
All points in the table must be plotted on the graph. These points must be plotted
accurate to half a small square.
No awkward scales should be used for the axes.
To plot the line of best fit, there must be an equal number of points on either side of the
line.
When calculating the gradient of the line, this must be demonstrated with a triangle on
the graph. The hypotenuse of the triangle must be greater than half the length of the
drawn line.
To calculate the y-intercept there are 2 options. Read-off from the intercept on the graph
or substitute into y = mx + c.
Then a different equation will be given, we must compare it with the general one - y =
mx + c and accordingly give the values and corresponding units for the different
variables.
Example Template of a table & Graph:
 Question 2 – “Inaccurate Method”: identify problems with method
& suggest improvements
Measure and record variable as asked. If a micrometer screw gauge is used record
to the nearest 0.01 mm e.g., 0.21, 0.29.
Take at least 3 readings and use the average as the final answer do NOT forget to
indicate appropriate units used.
With the use of a ruler to record measurements a precision of 1mm should be
used e.g., 15.4.
Uncertainty in a particular variable can be half the range between repeated
readings or it should be the smallest division of the measuring device.
The justification of the number of significant figures used in a particular variable,
should be linked to the number of significant figures used for the other variables
asked to be measured in the experiment which were ultimately used to calculate
it.
An example response would be: “Since the number of s.f. used in A and B were
2, then for accuracy purposes, the same number of s.f. should be used for C” This
answer should relate to all raw readings.
To explain whether the previous results of the 2 values of k support the suggested
relationship we must test it against a specified criterion.
An example response would be: “The percentage difference between the two k
values is greater than 10%, therefore this shows that the constants are not within
the limits of experimental accuracy. So, the relationship suggested is not
supported by the results obtained”.
To calculate the percentage difference between the 2 values of k use:
Kmax – Kmin/Kmin x 100%
e.g.

Sources of uncertainty or limitations of the procedure for this experiment:
There is one that can always be used for every single experiment:
 Two readings are not enough to draw a valid conclusion.
To make this part of the exam easier, we should keep taking notes on the side of the
exam while carrying out the experiment, every time we find something hard to
perform/measure/see etc.
e.g., of sources of uncertainty or limitations according to experiment performed
 Force & Newton-meter Experiment
 Oscillations of an object Experiment
 Equilibrium of an object/ruler Experiment
 Wave Experiment – investigating stationary waves

Improvements that can be made to this experiment:
There is one that can always be used for every single experiment:
 Take many readings and plot a graph or obtain more k values and compare.
To make this part of the exam easier, we should think about how it could have been
easier for us to perform/measure/see etc. something that we were asked to do,
relating, of course, to the sources of uncertainty or limitations that we have
previously identified.
e.g., of sources of improvements according to experiment performed.
 Force & Newton-meter Experiment
 Oscillations of an object Experiment
 Equilibrium of an object/ruler Experiment
 Wave Experiment – investigating stationary waves