According to the principles of quantum mechanics, at the microscopic level, the behavior of particles and systems is probabilistic rather than deterministic. This means that even when two objects, such as two balls with the same mass and volume, are subjected to identical conditions, their outcomes can still vary each time.
When dealing with macroscopic objects like balls dropped from the same height, the probabilistic nature of quantum mechanics typically becomes negligible due to the large number of particles involved and the statistical averaging that occurs. The behavior of macroscopic objects can often be described accurately using classical physics and deterministic equations.
In practice, if you were to drop two identical balls from the same height in the same way, you would expect them to behave similarly and reach the ground at roughly the same time. However, small differences in initial conditions, air resistance, imperfections in the balls themselves, and other factors could lead to slight variations in their motion.
While quantum mechanics provides a fundamental description of nature at the microscopic level, it does not necessarily dictate the behavior of macroscopic objects in a directly observable way. Classical physics, with its deterministic laws, is often sufficient for practical purposes when dealing with macroscopic objects in everyday life.