Abstract
We present a simple laboratory activity for introductory-level physics
students which involves rolling balls down pipes and analysing their
subsequent flight trajectories. Using balls of equal size but different mass
allows students to confront their misconceptions of a mass dependence of
the exit speed of the balls from the pipes. The concepts of conservation of
energy and projectile motion are also utilized as students analyse their data
graphically. Adding in concepts of rotational motion improves the
predictions. This is a safe and inexpensive laboratory exercise that allows
students to clearly see the power of model predictions in understanding the
behaviour of physical systems.