The aim of this activity is to find out which of the following 3 variables affect the period of a pendulum: mass of the bob, length of the string and frictional force.

The period is the time for one complete oscillation.

Complete this activity using a simulation.

You will need a length of string about 50 cm long.

Various objects of different masses. Find objects around you that can be tied to the end of the string.
A digital timing device such as a stopwatch or your phone.
A place to hang the string with the weight so that it can oscillate freely without any disturbance.
See picture below on how you can set this up at home. Experiment 1 – Investigating the effect of changing mass on the period of a pendulum

• For this experiment keep the length of the string at 50 cm.
• Attach different objects at the end of the string. The objects must be of different masses. If you have a scale, you can determine the mass by measuring them. If not, use your judgement to order the objects by increasing weight. Use can use a stone, a piece of wood, an eraser, and a piece of chalk to get different masses.
• Gently move the object to one side, try to estimate it to the same amount every time, and let the object swing from side to side.
• Use your timer to calculate the time for 10 complete oscillations then find the time for 1 oscillation.
• Fill in the table below. If you are unable to calculate the mass of the object, simply write what the object is in the table. Order by increasing weight.
 Mass / kg stone wood eraser chalk Period / s

Experiment 2 – Investigating the effect of varying lengths on the period of a pendulum

• For this experiment pick one of the masses, such as the stone from Experiment 1 and use it.
• Gently move the stone to one side and let the object swing from side to side. Ensure it doesn’t wobble.
• Use your timer to calculate the time for 10 complete oscillations
• Find the time for 1 oscillation and record it in the table below
• Repeat this for the different length of the string listed in the table below.
 length / cm 10 20 30 40 50 Period / s

Experiment 3 –  – Investigating the effect of varying amounts of friction on the period of a pendulum

• For this experiment keep the length of the string at 50 cm.
• Use the  stone or another object from experiment 1.
• Use a tank/container filled with water and allow the stone to oscillate in the water. (See pic below)
• Use your timer to calculate the time for 10 complete oscillations then find the time for 1 oscillation.
• Repeat using a tank of a different fluid e.g. oil if possible
 Friction Air Tank of water Tank of oil (optional) Period / s

Which variable affects the period of the pendulum?

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