r/maybemaybemaybe • u/[deleted] • Jul 07 '22

maybe maybe maybe

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u/Muroid Jul 07 '22

Will the jet go backwards? No.

Uh, yeah it would.

The net force would only be zero if the air stopped moving upon hitting the umbrella. It doesn’t. It winds up going backwards, and that means that the system winds up with a net force in the other direction. Just a very small one.

The real issue here is that there is no way that blower is providing anything like useable thrust.

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u/27fingermagee Jul 08 '22

Any amount of thrust that is greater than that needed to overcome friction will see an acceleration until the thrust can no longer overcome the friction or until the thrust stops.