start stop pendulum
Tie a 3 or 4 foot length of string between the backs of two
heavy chairs. Stretch the string as tight as possible. Tie a
large washer or other weight to one end of each of two 2 foot
long pieces of string. Tie the other ends of these strings to
the string between the chairs. Space them about a foot apart
and about a foot from each chair. The weights should not touch
the floor. Pull one of the weights to the side about a foot
and release it. After a short while you will notice the
stationary weight beginning to move and the swinging weight
moving less. Eventually the weight that you started swinging
will stop and the other weight will be swinging fully. This
trading turns will continue until friction gradually expends
the energy of the system.