MadSci Network: Physics |
Jim, I'm certainly inclined to agree with you. Yes, there will certainly be friction on the sphere as it rises through the water, but I don't think that the sphere would heat so much as to melt rubber or bake the scientist inside (though you're right...I don't think I'd want to try it!). You can compare the ascent of this craft through the water to a person sky diving. Of course water is much more viscous than air, but alot of the mechanics will work in the same way. A sky diver will feel the friction of the air on his body as he falls, but at the same time that air will be blowing past him and cooling him the whole way. He will also reach a maximum speed of descent as the force of the air resistance becomes equal to the force of gravity on his body. The same will happen to the sphere. Friction of the water along the sphere will create heat, but not much. As the water rushes past the sphere, it will certainly cool it, and I'm sure this cooling will occur much faster than frictional heat can build. Temperatures at the bottom of the ocean are around 34 deg F. In other words, just above freezing. Temperatures near the surface are probably going to be around 60-70 deg F. Water is a great coolant, so I would definitely say that it's probably going to be pretty cold inside that sphere, not the opposite. The sphere will also reach a maximum speed when water resistance equals the buoyant force. (Extra physics info: The buoyant force will be equal to the weight of the water that the sphere is displacing, minus the weight of the sphere. The resisting force of the water will be proportional to the square of the speed at which the sphere is moving. Thus the craft will accelerate due to the buoyancy until the increasing resistance is equal to the buoyant force, and it reaches a maximum speed) Hope that helps you. - Mike "Mad Scientist" Scannell
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