Page 195 - Physics

Linear motion

Acti vity 8.4

Aim: To determine the acceleration due to gravity using a simple pendulum
bob.

Materials: Retort stand, stopwatch, clamp, thread, metre rule, and pendulum bob

Procedure
1. Measure 90 cm of a thread by using the metre rule. Tie the bob to one end of the
thread and suspend the bob from the retort stand so that it swings freely.
2. Displace the bob through a small angle sideways and release it so that it oscillates.
3. Record the time taken for 20 oscillations using the stopwatch.

4. Repeat step 3 thrice.
5. Repeat steps 1- 4 for a thread of length l = 80 cm, 70 cm, 60 cm, and 50 cm.
6. Tabulate the results in the following table.

Length, Time, t for 20 Average time, t (s) Periodic T 2 T 2 Acceleration
l (cm) oscillations time, T (s ) l due to gravity,
2
t = t 1 t + 2 t + 3 t g m/s 2
3 T = 20

90 t 1 t 2 t 3
80
70
60
50

Questions
(a) Use a table similar to the one shown above to calculate:

(i) the average time for 20 oscillations.
(ii) the average periodic time, T (time for one oscillation).

2
(b) Plot a graph of T against l and calculate its slope.
(c) What is the nature of the plotted graph?
(d) Calculate the acceleration due to gravity, g using the formula,

g g = 4 2 p l
T 2
(e) Calculate the percentage error in an experimental value of g.

( Accepted value Measured- ) value
Percentage error = ´ 100.
Accepted value

189

Physics Form 1 Final.indd 189 16/10/2024 20:58