# Measuring Acceleration due to Gravity using a simple Pendulum.

Measuring Acceleration due to Gravity using a simple Pendulum

Simple Harmonic Motion is very similar to the motion of a bob of a simple pendulum. A simple pendulum is made of a metallic bob suspended by fine string. Using these apparatus the acceleration due to gravity had to be measured. The acceleration due to gravity on earth is 9.81ms-2, therefore every second the particle will increase it’s speed by 9.81ms-1. Although, this may not be the case, due to air resistance.

Acceleration is directly proportional to force and acts towards a fixed position.

## Planning

To derive a value for g, the S.H.M. equation was used:

For calculating ‘g’ the formula had to be rearranged:

T2 = 4π2 l

g

Therefore:

g = 4π2 l

T2

Where: g is the acceleration to gravity; T is the period & l is the length.

Out of the above, the length of the pendulum had to be measured and then the period with that information. Instead of using the formula, a graph could be drawn of length against T
2, calculate the gradient, invert it then multiply by 4π

g =
4π2 l

T2

“”””“””””.. all the weight is at the centre of the bob… - measuring to middle of bob. Keep bob small and dense is important….”””””

5b in analysis.. line of best fit – reason for lack of accuracy – strings got a weight therefore centre of gravity of whole pendulum will not be centre of bob.. Length of pendulum will be shorter than what measuring…”””””””””””

Apparatus

To measure ‘g’ using simple harmonic motion the following apparatus were used:

• Metre Rule
• Metallic Bob
• Fine string
• Clamp stands & clamps
• Split Cork (to hold string)
• Digital stopwatch
• Linear graph paper

They were set up in the following way:

The pendulum should have swung no further than 10° from the vertical.

The experiment was repeated three times to retrieve a more accurate result and twelve readings were recorded over 1.2m.