Three swings of varying height are suspended here. Sit on each swing and oscillate. Note down the time taken for a single oscillation in each swing using the stop clock provided.

What did you observe? 
The longer swing oscillates slowly and the shorter swing oscillates fastly.

The science behind it :
From the time taken (T) for a single oscillation , we can calculate the frequency= 1/T for all the three swings. Observing this, we can conclude that for a simple pendulum, frequency is inversely proportional to its length. Here the swings act as simple pendulum of varying lengths.