Mechanics - Simple pendulum - Experiment 1

EXPERIMENT NO. 1

The aim of this experiment is to determine the acceleration due to gravity using a simple pendulum.
You are provided with a thread, pendulum bob, metre rule, cork, retort stand and a stop watch or stop clock. Hang the pendulum bob on one end of 100-cm length of thread and clamp the other end firmly on the retort clamp using cork. The clamp should be fixed at the edge of the laboratory bench as shown in side and front view diagrams below.

Pull the pendulum bob aside at a small angle so that it swings with small amplitude. Find the time t for 20 oscillations as it swings from point A via C to D. Repeat this procedure with the lengths of thread of 80cm, 60cm, 40cm and 20cm. 

Tabulate your results including the column of period T (second) and T

Length L (m)	Time t for 20 osc (s)	Period T(s)	T2(s2)
1.0
0.8
0.6
0.4
0.2

a)   Plot the graph of lengths L(m) of the thread against T²(s²)

b)  Find the slope of the graph

c)   Using the relationship $$T={2π}\sqrt{l\over g}$$ Find the value of acceleration due to gravity g

d)   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