EXPERIMENT NO. 3
The aim of this experiment is to find the acceleration
due to gravity g and the ratio Q defined in part (d) by using a simple
pendulum. Suspend the pendulum bob with its upper part of the string fixed on a
retort clamp as shown in figure below. Make a knot Nat a distance of L =10cm
from the bob B. While X is the distance between the point of suspension S to a
knot N on the string Set X=60cm and pull the bob aside at a small angle so that
it can start swinging vertically
(a) Record the time t for 30
oscillations of the pendulum bob
(b) Repeat the above procedure
for the values of X= 50, 40, 30, 20 and 10cm and record all the time t for each
respective oscillations and calculate the period T. tabulate your results as
shown below
A TABLE OF
RESULTS
Length X (m)
|
Time t for 20 osc (s)
|
Period T(s)
|
T2(s2)
|
0.6
|
|||
0.5
|
|||
0.4
|
|||
0.3
|
|||
0.2
|
|||
0.1
|
(c) Plot a graph of T2
against X
(d)
(i) Find a slope S of the
graph
(ii) From the graph read and
record the value of T2 when X =0
(e) Evaluate Q where $$Q={T^2\over S}$$
(f) Find the acceleration due to
gravity g given acceleration due to
gravity g given that $$g={4π^2\over S}$$
(g) 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
SOURCES 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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