Giant Pendulum
A giant pendulum is a very useful prop to have as part of a show about motion or energy.
We constructed a pendulum from a 16lb ten-pin bowling ball. These balls are constructed
from a plastic resin and can be drilled and tapped relatively easily. The finger-holes can be
filled with plaster and sanded at the surface. If the ball is sprayed a metallic grey colour, it
can appear like a huge lead shot from a distance.
We suspended the ball using 3mm steel twine cable forming a V-shape suspension as shown
to prohibit out of plane motion. The entire arrangement is suspended from a strong support!
As well as the usual demonstrations of simple-harmonic motion and pendulum timing, it
is also useful for explaining the concepts of energy transformation and conservation.
The pendulum length can be arranged so that when pulled back over a couple of metres
of floor, it is at about head height. By bringing the ball to the point of a volunteer's nose
and letting it go, the idea of energy loss through friction at the pivot can be very visually
demonstrated, since the ball should come only within a cm or so of the nose on the return trip,
much to the relief of the volunteer!