`PendulumsJohn J. Miller                 Maine East High School                               6801 W. Dempster                               Park Ridge IL 60048                               (708)825-4484Objectives:The students will be able to determine what factors effect the period (timeto swing back and forth) of a Pendulum.  I use this for my sophomores in high school but don't let that fool you.  This can be used at any level where students can count to twenty and time something. Materials Needed:pinsvarious lengths of stringwashers (or any of various weights to hang)clock with second hand (or anything to time with)a long piece of cardboard or cork-board with a number-line marking off every    five seconds for up to one hundred seconds Strategy:Tell the students to grab a length of string, tie a washer to one end and a loop at the other end of the string.  Next have the students time the period of twenty swings.  Have the students hang their washer at the spot on the number line that corresponds with the time they have found.  There should be a pattern that looks something like this:                    | |  |  | | | ||      O O  |  | | | ||           |  | | | ||           O  | | | ||              | | | ||              O | | ||                | | ||                | | ||                O | ||                  O ||                    ||                    ||                    O|                     OAsk the students what factors would affect the period of the swing.  With encouragement, I bet they'll come up with length of string, mass, amplitude (how wide an arc), whether the hand moves or not, and possiblely some others.  Break the students up into groups and have each group investigate these factors by keeping all factors constant except the one they are investigating.  Have each group report back to the class with their findings. Performance Assessment:The verbal report to the group may be graded.  I believe the ideas of particularinterest include whether or not the group controlled the variables, did they actually make accurate measurements and present the data (not just guess or approximate) and then the actual presentation. Conclusions:1. Mass of the hanging objects does NOT make a difference.2. The amplitude does NOT make a difference (for amplitudes less than 40    degrees).3. Length of the string DOES make a difference.  There is a formula if you   wish to check it.  (Period=2(3.14)Square-root(Length/gravity) or     T=2pi*sqrt(l/g))4. Small hand movements do not make a difference extreme hand movements will.Reference:     Me! Call me anytime for help.`