Helium Balloon in Free-Falling Elevator · CAP 2002 #1
Physics · mechanics
Problem
A little girl is holding a helium-filled balloon on a string while riding in a closed elevator going down a very tall building at constant speed. The elevator shaft is maintained under vacuum. Suddenly the elevator cable snaps, sending the elevator into free fall. In her surprise the girl lets go of the string. She is even more surprised to see
(a) the balloon rising.
(b) the balloon floating downward.
(c) the balloon remaining stationary.
(d) the balloon bouncing slowly between the floor and the ceiling.