Page 23 - Physics

Introduction to Physics

plotted with a symbol which can be (h) In an exponential graph, a best fi t line
easily seen, e.g., a cross or circle. should be drawn by using freehand.

(e) A best fi t line should be drawn to the After recording and analysing the data,
graph. Do not start the graph at the you may look for possible trends or
origin unless there is a data point for patterns and explain why they occur that
(0,0), or if the best fi t line runs through way. For instance, physicists may notice
the origin. that as the length of the string to which
(f) If there is more than one set of data the bob is attached increases, the time to
drawn on a graph, a different symbol complete a given number of oscillations
also increases. This pattern forms the
(and/or colour) must be used for basis on which evidence can be obtained.
each set and a key or legend must be
included to defi ne the symbols. 6. Drawing a conclusion
(g) Use line graphs when the relationship A conclusion is a summary of the result
between the dependent and of the experiment. It includes a statement
that either proves or disapproves of the
independent variables is continuous. hypothesis. For instance, ‘the length of

For a line graph, you can draw a line the string to which the pendulum bob
of best fi t with a ruler. Make sure the is attached affects the time taken by a
number of points are distributed fairly pendulum to complete a given number of
and evenly on each side of the line. oscillations’ proves our hypothesis. The
experiment may be repeated to make sure
Example of a graph of square of the the results obtained are reliable.
period,   against length  
T
2
2
m
l
s
is shown in Figure 1.20. Example 1.6
A physics student conducts an
experiment to investigate the
2
T (s )
2
A relationship between the force applied
to stretch a spring and the resulting
displacement. The student collects the
following data:

B Table 1.3:
C
Force applied Displacement
(newtons, N) (centimetre, cm)
1 2
2 4
O l (m)
3 6
Figure 1.20: Graph of square of period, 4 8
T (s ) against length, l (m) 5 10
2
2
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