cliffrailwayThe cliff railway is powered by gravity. Using a construction kit like LEGO, can you model a counterbalanced lift system?
Your system should have two cages on which you can put small weights. Put some weights by hand into the lower cage, then add weights to the higher cage so that it pulls the lower cage to the top.
Note to teachers: This is not an easy task and might lend itself to an after-school engineering club.