For making a stethoscope with paper cup and plastic tube you require :-
plastic tube,paper cup,aluminium foil,tape and fevicol.
First make a hole in the bottom of the cup and cut out a circle of same size of that plastic tube. Tear off aluminum foil and roll it around the tape, taping it down the ends. Fit the plastic tube into the hole at the bottom of the paper cup and stick it with fevicol.