In this experiment, you are going to keep the mass and the angle the same, so they will also be controlled variables.

You will change the length of the pendulum. This is the independent variable. Then you'll measure the period, which is the dependent variable.

You can print this page to use it while you're doing the experiment.

Changing the Length

Decide what angle you will use to set the pendulum swinging. Mark it on the wall behind the release point.
Set up the full length of string with one weight on the end.

Trial 1:

Draw the weight back to the marked angle and allow it to swing for five full periods (over and back, 5 times).
Time how long it takes to do this.
Then divide your answer by five, to get the time for one full period.

Repeat this twice more. Don't forget to divide by five each time ... we want the time for one period.

Now average your three answers. If you have printed this page, record your answer here:

LONG STRING:   Average time for one period: ____________

Trial 2:

Retie the string at the top so it is about a third shorter.
Draw the weight back to the marked angle and allow it to swing for five full periods (over and back, 5 times).
Time how long it takes to do this.
Then divide your answer by five, to get the time for one full period.

Repeat this twice more. Don't forget to divide by five each time ... we want the time for one period.

Now average your three answers. If you have printed this page, record your answer here:

MEDIUM STRING:   Average time for one period: ____________

Trial 3:

Retie the string at the top so it is half as long as the previous trial.
Draw the weight back to the marked angle and allow it to swing for five full periods (over and back, 5 times).
Time how long it takes to do this.
Then divide your answer by five, to get the time for one full period.

Repeat this twice more. Don't forget to divide by five each time ... we want the time for one period.

Now average your three answers. If you have printed this page, record your answer here:

SHORT STRING:   Average time for one period: ____________

By now you should have data that will lead you to a conclusion. You might want to write your conclusion here:

When you change the length of a pendulum, the period ___________________________.

The shorter the string, the _____________________ the period.


If you would like to see the answer, open this page.


To see the equation that determines the period of a pendulum, visit this page.



Pendulum Experiment | Variables | Experiment 1 | Experiment 2 | Experiment 3 | Equation



Resources