how would you define a freely falling body? Is a ball throw upward considered as a freely falling body?

Answer 1

Yes, the ball thrown upward is a freely falling body when it stops going up and starts coming down!

While the ball is going up, it is acted upon by the earth's gravity which is acting in an oppoiste direction to the motion. Thus it loses momentum and finally stops at a height and starts falling back towards earth.

Answer 2

Technically the downward motion of the above mentioned body will not qualify as a free fall, because free fall is defined as the motion influenced only by gravity. An atmospheric fall involves deceleration due to drag and so it cannot be called true free fall!

Answer 3

If you neglect the influence of air drag (ball of high density such as lead) then your ball will be in free fall as soon as you release it from your hand after you accelerate it upwards. The free fall does not start at the highest point of the parabola but already when the ball leaves your hand.
Free fall is the state of local weightlessness inside the ball when it can move unrestricted according the acting inertia and force of gravity.

Answer 4

Theoretically it is a free fall but we have to consider that resistance restricted to it. Free fall is motion with no acceleration other than that provided by gravity. This also applies to objects in orbit even though these objects are not falling in the usual sense of the word. Strictly speaking nothing falling through an atmosphere can be in free fall due to the inherent resistance to motion, however in skydiving, the term is also applied to the period of the jump before the parachute is opened, and in colloquial usage, falling through an atmosphere is normally considered to be free fall.