Why light and heavier objects when fall through vacuum move side by side?

Answer 1

Relevant formulae:

weight = mass x gravity

force = mass x acceleration (Newton's Second Law)

Let's say, for the sake of argument, that one object has twice the mass of the other. For example, 2 kg versus 1 kg. The more massive object will be subject to twice the gravitational force - close to Earth's surface, that would be about 20 newton, compared to 10 newton for the less massive object. But the more massive object also has twice as much inertia; that is, twice the force divided by twice the mass will provide the same acceleration.

Answer 2

In a vacuum, there is no air resistance to affect the motion of objects. Thus, both light and heavy objects will fall at the same rate, accelerating towards the ground due to the force of gravity. This principle is known as the equivalence principle, as stated in Einstein's theory of general relativity.