Answer: The force of gravity due to the earth acts on each and every object, hence, when we are holding a stone in our hand, the stone experiences this force. Nevertheless, it is balanced by another force that we apply to it in the opposite direction. The result of this is that the stone remains at rest. However, when we release the stone in our hands, the only force that acts on it is the gravitational force of the earth and the stone falls down by its influence. Any object that moves under just the influence of the force of gravity is falling freely. Thus, this released stone is in a state of free fall. The initial velocity of the object during the free fall is zero, which increases along with the acceleration resulting from the gravity of the earth. In free fall, the frictional force due to air opposes the motion of the object and a buoyant force is also applied to the object. Hence, free fall is only possible in a vacuum.
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