Making a model hydraulic elevator
Some freight and passenger elevators are increased by water pressure. You can make a model of one of these with an automobile hand pump. Connect the tube from the pump to a length of rubber tube. Bind the connections with wire so they will not blow out. Now connect the tube to a water tap with a one-hole rubber stopper. Again bind the connection of the tube and stopper. Steady one of your pupils as he sits on the handle. Turn the water on slowly and see if the water pressure will raise him. You might be have to hold the stopper in the tap.