EXPERIMENT NO. 4
You’re required to determine the height of the laboratory
bench and the acceleration due to gravity g.
Proceed as follows;
(a) Tie one end of the pendulum
bob to the pendulum bob and fix the other end of the thread to the edge of the
bench with a small nail keeping the height from floor to the pendulum bob as h
= 5cm as shown in figure below
(a) Displace the pendulum
through a small angle to one end and set it to oscillate with small amplitude.
Record the time for 30
oscillations hence determine the period T for one complete oscillation.
Increase the height h above the
floor by 5cm interval such that you obtain four other values of h and repeat
the procedure in (b) above
(b)
(i) Tabulate your results
(ii) Plot the graph of T2
(y- axis) against h (x- axis)
(iii) Determine the slope of the
graph and find the acceleration due to gravity g using the relation$$T^2={-4π^2 h \over g}+{4π^2 H \over g}$$
(iv) Determine the height H of the bench
(a) State all possible sources
of errors in this experiment and state the precautionary measures that are to
be taken in order to reduce the effect of those errors
SOURCEES OF ERRORS
IN THE EXPERIMENT
Environmental sources
Wind resistance to the oscillating motion of a pendulum
bob
Measurement sources
i) Errors in measurement of
length which may include parallax and zero error of the measuring devices
ii) Error in timing device like
stop watches (errors in starting and stopping a stop watch)
iii) Large angle of displacement
of the bob which may disturb to and fro movement of the bob
Graphing error
i) Uses of blunt pencil in
drawing graph
ii) Too much estimation when
drawing graph
iii) Taking very close points
when calculating slopes from graph
PRECAUTIONARY MEASURES IN REDUCING THE EFFECTS OF
ERRORS
i) Conduct the experiment in a
part of the laboratory free from drought
ii) Zero error of the metre
rule should do be treated
iii) Angle of displacement of
the bob should be kept as small as possible
iv) Sharp pencil should be used
in drawing graph
v) Choose far point when
calculating gradient
vi) Repetition in taking data
and uses of average data should be done
vii) Avoid unnecessary
estimation of data or truncation
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