Conversation

I have a mechanical engg. question that I could ask my dad but he's 7 hours ahead of me Consider this zany contraption Would it take less energy to drive the last gear underwater than it would above? Can we construct a gearbox that arbitrages gravity?
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I see no reason it should. The inertia of the gear train would not change. You’d just add extra resistance. It should get marginally harder actually.
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ah damn...liquid resistance.... In principle tho if there were a gravity differential between the ends of the gearbox, are we doing something interesting or am I misunderstanding something other than basic laws of thermodynamics?
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Gravity is kinda irrelevant here. Inertia is rotational. I don’t see what you’re getting at tbh. Something like a space elevator arbitrages gravity in a way.
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Buoyancy doesn’t change rotational inertia. This would be as hard to move in free fall/microgravity as well. You’re not doing work against gravity. Your work is turning into rotational kinetic energy.
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If each gear has moment of inertia I, and you spin up the last gear to ω rad/s, the gear-train energy is: 0.5*I ω ²*(1+4^2+ 16^2....) I see no way to cheat that. Conservation of energy.