Impetus may wear out or be overcome. A great many students and adults believe that a thrower imparts a
force to a projectile that stays with it and is the cause of continuing motion. Although they may use a term
such as "energy," "force," or "acceleration," the concept is very similar to the medieval idea of impetus.
The curving shape of a trajectory is then explained as gravity "takes over" and impetus dies away or is
overcome by the gravitational force.