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The aim of this assignment 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.
To complete the assignment you can either use real equipment or use a virtual simulation located at the following link: http://phet.colorado.edu/sims/pendulum-lab/pendulum-lab_en.html.
Try this link if you have trouble accessing the previous one. http://phet.colorado.edu/en/simulation/pendulum-lab
It would be good to find a partner to complete this with.
If using virtual simulation go to Option A - Virtual Simulation. If using real equipment skip to Option B - Real Equipment.
Option A - Virtual Simulation
You will use the simulation located at the link above. Spend about five minutes working with the simulation and locating the sliders to control the mass of the bob, the length of the string and the friction. These are highlighted in the screenshot below.
Check the box that has the label Photogate timer. The photogate timer will easily measure the period of the pendulum because it has a high degree of accuracy.
Experiment 1 - Investigating the effect of varying masses on the period of a pendulum
For this experiment keep the length of the string at 2 m and set friction to none.
Click the blue mass and drag it to the side until it is at an angle of 15 degrees. Release the mouse to allow the mass to fall.
Click start on the photogate timer and record the period in the table below. Repeat this for all the masses in the table.
Experiment 2 - Investigating the effect of varying lengths on the period of a pendulum
For this experiment
Set the length to 0.50 m
Set the mass to 1 kg
Uncheck 'Show 2nd Pendulum'
Set friction to none.
Select real time and set the planet to Earth
Check the box that has the label Photogate timer
Click the blue mass and drag it to the side until it is at an angle of 15 degrees. Release the mouse to allow the mass to fall.
Click start on the photogate timer and record the period correct to 2 decimal places in the table below. Repeat this for all the lengths in the table. Do not change the mass while you are repeating the experiment. Ensure to only change the length.
Plot a graph of T (y-axis) vs l (x-axis).
Now plot a graph of T2 vs l.
Compare the general trend of the points
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 2 m and keep the mass at 1 kg.
Click the blue mass and drag it to the side until it is at an angle of 15 degrees. Release the mouse to allow the mass to fall.
Try it for the three values of friction in the table below
Which variable affects the period of the pendulum?
Option B - Real Equipment
You will need a length of string about 50 cm long
Various objects of different masses. Find object 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 weights. 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, simple write what it is in the table (as shown in the table)
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, 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.
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 from experiment 1
Use a tank/container filled water and allow the stone to oscillate in the water. (See pic below) The water will provide more frictional force that in air. If you can obtain a large amount of another fluid that is more viscous than water (such as oil) feel free to try a third time using oil.
Use your timer to calculate the time for 10 complete oscillations then find the time for 1 oscillation.
Which variable affects the period of the pendulum?
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