  Projectile motion is a constant theme in introductory-physics courses. It is
often used to illustrate the application of differential and integral calculus.
While most of the problems used for this purpose, such as maximizing the range,
are kept at a fairly elementary level, some, such as determining the safe
domain, involve not so elementary techniques, which can hardly be assumed of
the targeted audience. In the literature, several attempts have been undertaken
to avoid calculus altogether and keep the exposition entirely within the realm
of algebra and/or geometry. In this paper, we propose yet another non-calculus
approach which uses the projectile's travel times to shed new light on these
problems and provide instructors with an alternate method to address them with
their students.
