The purpose of this exercise is to explore how changes in one variable (length or weight of a pendulum) affect another variable (period of a pendulum). In other words, we will consider the period of a pendulum as a function of the length and weight of the pendulum.

Period as a function of weight

Construct a pendulum by hanging a washer from a paperclip, then tying the paperclip to a piece of string hung from a desk. You will want to shorten your pendulum several times for the next step of the experiment so make the pendulum as long as is convenient. Working as a group, find out how long it takes the pendulum to swing back and forth ten times. Record that value in the table below. (For best results your pendulum should swing through an arc only a few inches long.) Once you have practiced finding the time for ten swings with one weight, add more washers to the pendulum and find the time it takes to make ten swings with two or three weights attached.

Number of washers	1	1	1	2	2	3	3
Time for 10 swings
Time for 1 swing = Period

1. In this experiment, what is the independent variable? What is the dependent variable?

    

2. Use the grid below to plot your results showing the number of washers along the x-axis and the period (time for one swing) along the y-axis.

   

3. How do you think the period of the pendulum is related to its weight?

    

    

    

    

    

Period as a function of length

In this experiment, use only one washer to weight your pendulum and change the length of the string your pendulum hangs from. To find the length of the pendulum, measure the number of inches from the top of the string to the center of the washer. You may wish to do two trials for each length.

Length of pendulum
Time for 10 swings
Time for 1 swing = Period

1. In this experiment, what is the independent variable? What is the dependent variable?

    

2. Plot your results.

   

3. How do you think the period of a pendulum is related to its length? Be as specific as you can.