Move the suspension point with the mouse to start the oscillations.  Notice
how the oscillation amplitude decreases due to friction.  You can vary the
amount of friction using the F7 and F8 keys.  Use F3 and F4 to decrease or
increase the length (L) of the pendulum and F5, F6 to change the
gravitational acceleration (g).  To time the oscillations use the timer
displayed in the upper right corner.  Use F9 to turn the timer on, to turn
it off and to reset it.

Find out whether the period (T) depends on the amplitude of oscillation
for amplitudes smaller than, say, 20 degrees.  What happens to the period
for much larger amplitudes? What is the effect of changing g and L ?  How
does T change?  For example, what happens when g or L are made 4 times
smaller or larger?  See what the pendulum would do if g were negative.

Try to verify the law of pendular motion for small oscillation amplitudes: 
                   ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
                   ³  T = 2 * pi * sqrt( L/g )  ³
                   ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Measure and plot T as a function of L and of g.  To get a good measurement
of T, time a large number of oscillations and divide the time by that
number. Do your experimental results agree with theory?  Is there a formula
for large amplitude pendular oscillations? Try to find it and to verify it.