Finding the Acceleration of Gravity Using a Pendulum
Perform an investigation and gather information to determine a value for acceleration due to gravity using pendulum motion, computer assisted technology and/or other strategies and explain possible sources of variations from the value 9.8 m/s2.
Aim:
To determine a value for acceleration due to gravity from its effect on the motion of a simple pendulum.
Equipment:
string, ball, stopwatch, ruler.
Method:
1. Setup pendulum as shown above.
2. Determine the length of the string and ball with a ruler.
3. Angularly displace the pendulum out an angle < 15 and let it swing in one plane.
4. Using the stopwatch, determine the period of the pendulum by timing 10 oscillations and then dividing by 10.
5. Repeat steps 2-4 for 4 other lengths of string with 20cm more in length.
6. Repeat this 5 times.
Results:
Graph L Vs T2 has a linear relationship.
L is directly proportional to T2.
Average value obtained was 9.79 m/s2
Discussion:
A pendulum consists of a point mass, which has all of its mass concentrated at the centre, attached to a string with negligible mass that is fastened so that the pendulum can oscillate in one plane.
The independent variable is the Length (L).
The dependent variable is the Period (T).
The mass of the bob doesnt affect results.
The angular displacement (amplitude of swing) doesnt affect the Period (the result), provided that the angle < 15. The following formula can only be used for angles < 15.
Data collected is the period of swing. It is used in the formula for pendulum motion to determine the acceleration of gravity. The angle of swing was kept < 15, so that results could be kept accurate.
Inaccuracies were caused by human reaction time in using the stopwatch to measure the period, so more periods are timed and divided appropriately to reduce error margin. Measurement of the length wasnt accurate because it was difficult to measure it using a ruler. But both didnt have much affect in this lab, given the results.
Conclusion:
A value for acceleration due to gravity was obtained, using pendulum motion and the above formula for pendulum motion.
