He also divided motion into violent and natural, and claimed that any trajectory consisted of rectilinear and curved portions. The violent motion at the beginning of the blast is in a straight line at an oblique angle. The natural motion of the ball toward the Earth takes over and this transition results in a curve. Roughly a contemporary of Galileo, Bennedetti claimed the medium hinders, not aids, the motion. He also introduced the ideas of impetus, which became very important to Galileo as well.
Impetus is a quality transferred to a body which enables it to have motion.
Galileo clarified and made the impetus theory more coherent. Using the example of heat and sound, Galileo explained impetus. If you strike a bell, it is given a sonorous quality that is transferred from the hand to the bell, though the sound continues even after the hand is removed. The sonorous quality is not natural to the bell, but is rather impressed upon it. However, it is unclear whether at this time he discovered that trajectories follow a parabolic path, althought many influential historians, including Stillman Drake, believe so .