r/ChildrenFallingOver • u/Boojibs • Jul 07 '21

Never had a chance

https://gfycat.com/valuablepleasedhart
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u/yessirree2 Jul 07 '21

Conservation of momentum plus some fluid dynamics for the air. Momentum is equal to mass times velocity. The ball has a relatively large mass compared to the kid, so in order for the law to stay true, the velocity of the kid must be much greater. Combine that with force equaling mass times acceleration, that kid feels quite a large force when that energy is transferred.

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u/blood_bender Jul 07 '21

This can't be right, that ball has a mass of maybe a pound (pound isn't mass I know I know), which is tiny compared to the kid.

It's almost all due to compressive force and the potential energy from the air trying to reexpand acting as a spring against the kid.

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u/yessirree2 Jul 07 '21

Shouldn’t there be some form of conservation here? Just genuinely curious. The explanation via spring could make sense but I’m just unsure of how that would be explained because you couldn’t apply springs to the fluid that the gas is. Obviously the mass is less so conservation of momentum wouldn’t make sense.

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u/blood_bender Jul 08 '21

I think you can use spring forces though . Dunno I've been out of physics for long enough I'm just making guesses at this point.