Question

How does Galileo inferred that objects in vacuum fall with uniform acceleration

Answer 1

In the period before Galileo, scientists believed that force causes speed. But Galileo showed that force actually acceleration. By using the law of parabolic fall, Galileo concluded that bodies fall with constant acceleration on the surface of Earth and that force of gravity which causes all bodies to move downward is a constant force. In other words, he reached the conclusion that a constant force does not lead to constant speed but to constant acceleration. This conclusion was later followed by a claim that a body continue its motion as long as no other factor disturbs its motion. This principle is called the Principle of Inertia.
Thus Galileo lay of fall claims that bodies fall at constant acceleration. It means that the speed of the body increases with equal increments within equal intervals of time and that the distance traveled by them in those equal time intervals is not equal.