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Free fall is any motion of a body where gravity is the only acceleration acting upon it.

But, what if I threw an object from a certain altitude, and had two jetpacks put on it , one providing acceleration vertically upwards, the other downwards such that the overall resultant acceleration due to the two jetpacks was zero, and the only resultant acceleration would be due to gravity.

Would this still be considered free fall?

Intutively, I think it should be, as acceleration due to gravity is the only NET acceleration acting on it.

However, the counter argument could be that the resultant of the other two vectors is zero, which although has no physical significance, is technically giving 0 acceleration to the object.

Help will be appreciated, thank you.

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I would agree with you that in your first example it IS still a technical free fall.

A free fall is according to what i've learned any motion of a body in which gravity is the only resultant force on the body.

So in your example, as long as the two forces from the jetpacks cancel out completely it should still be considered a free fall.

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  • $\begingroup$ Thank you, that explains it :) $\endgroup$
    – JakePaul
    Commented Aug 11, 2019 at 14:49
  • $\begingroup$ Wikipedia defines free fall as when gravity is the only force acting. $\endgroup$
    – ParadigmShift
    Commented Aug 12, 2019 at 3:15
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Your counter argument seems inconclusive for me since (only in your counter argument) you are forgetting about gravitation. In the counterargument you have THREE forces: Jetpack up, jetpack down and gravity. Jetpack up cancels with jetpack down, gravity is still there.

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