A vertical string with weights attached at spacings that correspond to increasing squares (4 inches, 9 inches, 16 inches, etc.) is dropped, either by the demonstrator or a member of the audience. The weights don’t need to be heavy, they just need to make a notable sound when they hit the floor. The sounds of the weights hitting the ground will occur at regular intervals.
Alternatively, or as a lead-in demonstration, drop a vertical string with weights attached at equal spacings. In this case the frequency of the weights hitting the ground will increase as the string falls. In both cases the longer the string is, the better the effect.
The geometric nature of the relationship between distance (d) and time (t) for constant acceleration is demonstrated, audibly. Since the string is starting from rest, d = .5gt2, where g is a constant (9.8 meters per second per second). The constant is irrelevant when units are of no concern, so the squares of members of any arithmetic sequence will work for the string with increasing spacing of weights.
This demonstration is best for smaller groups of mid-level students (some middle schoolers, high schoolers, and college freshmen). It is great for a visually handicapped audience; have one or more members of the audience verify the spacing of the weights before the string is dropped.
Shock Value: 2