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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