```PendulumsLisa Ingram                      Frederick Douglass Middle Academy                                 543 N. Waller                                 Chicago IL 60644                                 (312) 534-6176Objective:To determine the relationship of the frequency of vibration to the pendulum's length.Materials Needed:meter sticks (ring stands optional)tapestringobjects of similar shape but different sizes pendulum bobsstop watchescalculatorsStrategy:Presentation:         Ask students if they have ever seen a pendulum.  Make pictures available of different types of pendulums. Ask for two volunteers (a tall one and a short one).  Have these two people stand side by side.  Ask half of your class to count the amount of steps that the tall student takes.  Ask the other half to count the amount of steps the shorter student takes.  The two volunteers are to walk together (this is not a race).  Ask students to observe the results and discuss. (They should observe that the shorter person takes more steps than the taller student in order to keep up).  Discuss how the arm and the leg are pendulums.  The leg is attached and it goes back and forth when taking steps.  Discuss another type of pendulum that you see on a playground, the swing.  Discuss how the swing goes back and forth like a pendulum. (A picture of a swing is optional)  Part B

Preparation:Demonstrate to the students how to suspend the pendulum and how to count.  If necessary review the use of the stop watch.  Practice timing and counting a couple of times.Equipment: The same lengths of string (60cm), pendulum bobs, stop watches, meter sticks. Procedure: The class is divided into fours' for this activity.  There should be a designated recorder, timer, counter, and swinger. First, the class will be instructed to take one of the objects and tie a string around it. Second, they should be given a location to tape down their meter stick.  Third, the students can began to do the following:  The recorder has paper and pen and is ready to write.  The timer has the stop watch at zero and is ready to time. The swinger is holding the pendulum at a suspension and will let the timer know when he/she will release. The pendulum will be timed for 10 swings.  (This means that the timer hits the start button, when the swinger saids release.  The counter will begin counting 1 when the pendulum comes back toward he/she.)  Each group will do this 3 times.  The recorder will write down the times and then average them with a calculator. A chart will be written on the board for each group to write down their calculations or timed vibrations. Conclusion: Students should take note that all of their calculations are very close, if not the same. Part B:  The same groups will repeat the exercise above, however, they will use different lengths of string (20, 40, 60, 80, 100cm).  Each group will be given their lengths of string to make new pendulums.  They will begin timing 10 swings and recording.  This data will also be written on the board. (Students should began to see a difference in the calculations of the other groups vibrations).  The teacher will graph the timed vibrations on the board.  The vibrations on the x-axis and the length of string on the y-axis.   As an extra visual aide, the teacher can tape the actual pendulum of each group on the graph and discuss. Performance Assessment:Each group will be given two worksheets to complete.  On the first worksheetwill be two questions. They are the following:  1st - Compare your timedvibration calculations (by looking at the graph on the board) to the othergroups.  Write down your observations.2nd - Compare your timed vibrations again (by looking at the graph on the board) to the other groups.  Write down your observations.The second sheet will be done individually and it asks the following: - What affects the vibration of a pendulum?```