We already talked about simple harmonic motion a bit when we talked about circular motion, so we reviewed some terms for describing vibrations.  The period (T) of an oscillation/vibration is the time it takes for one complete oscillation to take place.  The frequency (f) of an oscillation is the number of oscillations per second, which is just the inverse of the period,  T = 1/f.  Lastly, we talked about amplitude (A) of an oscillation, which is how big the vibration is – how far from equilibrium it reaches.  So for a kid on  swing, its how far the swing goes from just hanging straight down and in this case you might want to measure amplitude with the angle of the swing.

IMG_1675We did two different experiments.  We used the air track and hooked up two springs to one glider so it oscillated back and forth in the  middle of the track. The students used the video physics app to record the motion.  The data was then transfered to Graphical Analysis app where they printed  a graph of the position of the glider vs time and could read off the amplitude and period of the motion.  Experiment-5.cmbl.They did this for different amplitudes and found the period was always 1.6 seconds.  Then they added mass to the glider and found the period of the oscillation increased with mass.

The other experiment involved a pendulum.  Students used stopwatchs (apps on the their ipads) to measure the time for 10 complete swings and then divided the whole time by 10 to get the period.  They took  data for different masses (lead, steel and wooden pendulum bob), for different amplitudes and for different string lengths for the pendulum.  They confirmed that the period of a  pendulum does not depend on mass or amplitude, but it does depend on the length of the string.

 

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