In this experiment, you are going to keep the angle and the string length the same, so they will also be controlled variables. You will change the amount of mass on the end 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 Mass Decide what angle you will use to set the pendulum swinging. Mark it on the wall behind the release point. Set up the pendulum with a length of string, and tie one weight to the end. Leave enough extra string below the tie point so that you can attach more weights later without changing the length of string above the weight(s). Trial 1: Draw the weight back to the release point, 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: ONE MASS:   Average time for one period: ____________ Trial 2: Add a weight, so that two are tied to the string. Don't change the length of string above the weight(s). Draw the weights back to the release point, and allow them 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: TWO MASSES:   Average time for one period: ____________ Trial 3: Add a weight, so that three are tied to the string. Don't change the length of string above the weight(s). Draw the weights back to the release point, and allow them 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: THREE MASSES:   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 mass on the end of a pendulum, the period _________________________________________ If you would like to see the answer, open this page. Now try the next experiment. Pendulum Experiment | Variables | Experiment 1 | Experiment 2 | Experiment 3 | Equation Resources