Determining Gravity with a Pendulum

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        SPH141        Practical 2

Practical Experiment 2

Determining Gravity with a Pendulum


To determine the local acceleration due to gravity using Galileo pendulum technique.


Gravity is a force that acts on Earth every day. Sir Isaac Newton was first to underline the principles of gravity when an apple fell on his head (Ashbacher 2002). He stated that each particle with a mass attracts all other particles with mass with a gravitational force that is directly proportional to the product of their masses and inversely proportional to their distance of separation squared (Ashbacher 2002).

This is due to that gravity acts between objects (Ashbacher 2002), consequently causing a force of attraction which pulls the two object together, such as that an object with a mass will fall down towards earth ground. The Earth’s mass creates a gravitational force, which pulls the object down towards Earth.  

This theory is also supported by Newton’s three law of motions, particularly the first law stating that, ‘an object in motion or at rest will remain in motion or at rest unless acted upon by an external fore‘. An object will remain at rest floating in the air, however since an external force, gravity, acts upon it, the object falls towards Earth.

Theoretically, the acceleration due to gravity on Earth is 9.8ms-2, however it can also be determined through the use of the equation;

T = 2π


T = time it took for the pendulum to cycle (s)

L = distance between pivot point and center of the pendulum (m)

g = value of acceleration due to gravity (ms-2)

In order to determine the acceleration due to gravity, the equation were to be arranged to

g =



Set up the pivot point location on the whiteboard as shown in the diagram 1.1 in appendix 1 by using the sticky tape to tape the whiteboard diagram hanger onto the magnetic whiteboard marker holder.

Sticky tape the marker holder 1.5m high, while making sure that the magnetic texture holder is immovable and secured.

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Using the measuring tape; measure out 90cm on the 2m string then using the scissors cut the string, while making sure that the string is cut above 90cm as some measurements are required for the purpose of tying.

Tie one end of the strong string onto the center of the pendulum and the other end of the string onto the pivot point (end of the whiteboard diagram hanger), while making sure that the actual length from the pivot point to the center of the pendulum is 90cm.

Using the whiteboard marker and ruler, rule a line directly ...

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