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Experiment14Pendulum PeriodsA swinging pendulum keeps a very regular beat. It is so regular, in fact, that for many years thependulum was the heart of clocks used in astronomical measurements at the Greenwich Observatory.There are at least three things you could change about a pendulum that might affect theperiod(thetime for one complete cycle):the amplitude of the pendulum swing (measured from the equilibrium position)the length of the pendulum, measured from the center of the pendulum bob to the point ofsupportthe mass of the pendulum bobTo investigate the pendulum, you need to do acontrolledexperiment; that is, you need to makemeasurements, changing only one variable at a time. Conducting controlled experiments is a basicprinciple of scientific investigation.In this experiment, you will use a Photogate capable of microsecond precision to measure the periodof one complete swing of a pendulum. By conducting a series of controlled experiments with thependulum, you can determine how each of these quantities affects the period.Figure 1OBJECTIVESMeasure the period of a pendulum as a function of amplitude.Measure the period of a pendulum as a function of length.Measure the period of a pendulum as a function of bob mass.Determine the effects of damping on amplitude, frequency, and period.MATERIALSProtractor (see course homepage)Yard/Meter stick or tape measureStringTiming device, precise to the nearest second.LIGHT, Plastic, ~500 mL water bottleTI-83/84 or similarPhysics with Computers14 – 19a9720ef003108da59499203416706b1614076a3.docLast printed 11/8/2011 12:12:00 PM
Experiment 14PRELIMINARY ASSIGNMENTRead §11.0 – 11.1. In your lab book, defineperiod,frequency,amplitude, andcycle.Read this lab. Create data & calculation tables in your lab book. Definecontrolled experiment.1.Make a pendulum by tying a 1-m string to a mass. Hold the string in your hand and let the massswing. Observing only with your eyes, does the period depend on the length of the string? Doesthe period depend on the amplitude of the swing?