Take Home Lab #1

Take Home Lab #1

Question:  Which variables affect the period of a pendulum?

Safety:  Do not swing the pendulum in a dangerous manner. Washers can be a choking hazard, so keep them out of the reach of children.

Materials: Thread or dental floss, washers, a timer

Procedure: In this lab, you will determine which of three factors determines the period of a pendulum. A pendulum is a weight hanging from a string. You will use a piece of thread or dental floss (approximately 50 cm) and washers to make your pendulum. The period is how long it takes the pendulum to swing back and forth once. The three factors, or variables, that you will test are the mass at the end of the pendulum, the angle from which the pendulum is swung, and the length of the pendulum. You need to follow the rules of a good experiment (i.e., changing only one variable at a time, repeating each trial more than once, etc.). This procedure will be determined by you but here are some ideas and tips:

1. Count your pendulum for 10 swings (back and forth is one swing) for each of your trials. Then use a timer to record how long it takes for those 10 swings.

2. You will need to make 27 total trials for this experiment.

3. You would first have to experiment with the angle of the swing—you would do three swings at a low angle, three swings at a medium angle and three at a high angle.  During those trials, you do not change the mass at the end or the length of the string, those must stay the same.

4. Then you could change the amount of mass at the end of the

string. Keep the length of the string the same and also the angle that you swing it at the same. You would need to do nine trials of

this, three trials with a heavy mass, three with a medium mass, and three with a lightweight mass.

5. Look for significant changes in your data, a time change of 1.2 sec to 1.5 sec is not a big change. But a change of 1.2 sec to 3.5 sec is significant.

1. Data charts: Because you will determine the procedure, you will also determine the data charts. You will need to make three data charts, one for the length of the string, one for the change in mass, one for the change in angle. Each data chart will have nine data points for that experiment.

For example:

Length of string	Trial #1	Trial #2	Trial #3	Average
Short string
Medium string
Long string

Post-Lab Questions:

2. Which variable or variables had the biggest effect on the period of the pendulum?

3. Can you relate this information to your experiences on or around playground springs? Explain.

4. Draw three bar graphs one for string length, one for angle and one for mass. Each graph should have the variable being tested on the x-axis and the period (time in seconds) on the y-axis. Start the y-axis at 0 sec to avoid amplifying small changes. Graph the average swing time for each of the conditions.