Physics - Kinematics Question with Solution | TestHub

According to Aristotle, when an object is removed from its natural place, it possesses a tendency to return to its place. Natural motion results from this tendency of an object to seek its natural place. Hence, fire (or smoke), being naturally light, would rise, whereas rocks, being naturally heavy, would fall. Furthermore, Aristotle asserted that any object, after it is released, quickly reaches some final speed which it maintains to the end of its path. When we pick up a stone and release it, the stone strives to return to its natural place, the earth, and quickly gains a speed that it maintains during its entire fall.

From the common observation that a heavy stone falls faster than a feather, Aristotle reasoned that mass is a factor that governs the speed of the fall. Consequently, the heavier an object, the greater would be its potential to return to the earth. In turn, this stronger tendency would cause a greater speed of fall. Aristotle's description of motion agreed well with common observations of falling leaves, raindrops, and stones. In all cases, the body encounters resistance to its fall from the air.

Galileo attempted to show that Aristotle's belief was logically inconsistent by the following argument. Consider two masses, $m$ and $M$, where $m<M$, joined together to form a double stone. Then, during the fall, $m$ should retard $M$, since it tends to fall more slowly when falling individually. So the combination would fall faster than $m$ but more slowly than $M$. However, according to Aristotle, the double body $(M+m)$ is heavier than $M$ and hence should fall faster than $M$.