- Inference : When the length of a simple pendulum increases, the period of oscillation also increases. // The period of pendulum is affected by the length of the thread.
- Hypothesis : The longer the length of a simple pendulum, the longer will be the period of oscillation
3. Aim : To find the relationship between the length of a simple pendulum and the period
4. Variable : a) Manipulated variable : Length, l
b) Responding variable : Period, T.
c) Fixed variable : Mass of pendulum bob.
5. Materials/ Apparatus : Retort stand, pendulum bob, thread, metre rule, stop watch.
7. Procedure :
a) Set up the apparatus as shown in Figure above.// A small brass or
bob was attached to the thread. The thread was held by a clamp of a
the retort stand.
b) The length of the thread , l was measured by a metre rule, starting
with 90.0 cm. The bob of the pendulum was displaced and released.
c) The time for 20 complete oscillations, t was taken using the stop
watch. Calculate the period of oscillation by using, T = t / 20
d) The experiment was repeated using different lengths such as
80.0 cm. 70.0 cm, 60.0 cm, 50.0 cm and 40.0 cm.
Length of string, l / cm
Time taken for 10
oscillation, t (s)
Period of oscillation
8. Plotting the graph
a) Plotting the graph
· The graph should be labeled by a heading
· All axes should be labeled with quantities and their respective units.
· The manipulated variable (l) should be plotted on the x-axis while the responding variable (T2 ) should be plotted on the y-axis
· Odd scales such as 1:3, 1:7 , 1:9 0r 1 :11 should be avoided in plotting graph.
· Make sure that the transference of data from the table to the graph is accurate.
· Draw the best straight line.
- the line that passes through most of the points plotted such that is balanced by the number of points above and below the straight line.
· make sure that the size of the graph is large enough, which is, not less than half the size of the graph paper or.( > 8 cm x 10 cm )
10. Discussion / Precaution of the experiment / to improve the accuracy
a) The bob of the pendulum was displaced with a small angle
b) The amplitude of the oscillation of a simple pendulum is small.
c) The simple pendulum oscillate in a vertical plane only.
d) Switch off the fan to reduce the air resistance
The length of simple pendulum is directly proportional to
the square of the period of oscillation. //
T2 is directly proportional to l (the straight line graph passing
through the origin)