Does a cube of aluminum yield in the sea?

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  • #1
hermtm2
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Homework Statement



A cube of aluminum is suspended deep in the ocean. Will it yield if it is placed deeper and deeper in the ocean?


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The Attempt at a Solution



I guess that it will yield since the pressure from water will be stronger as it goes deeper.



Thanks,
Ryan.
 

Answers and Replies

  • #2
CWatters
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No.

This is a solid block of aluminium right? The pressure inside is going to be the same as outside. You might be able to compress the aluminium very very slightly I suppose. However I think the temperature difference down there is likely to have a bigger effect on the volume of the cube than the pressure.
 
  • #3
hermtm2
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So the cold temperature prevents changes in volume?
I did not think about that.



Thanks,
Ryan.
 
  • #4
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No.

This is a solid block of aluminium right? The pressure inside is going to be the same as outside.
Not necessarily. If the pressure exerted by the water is greater than the repulsive force of the aluminum molecules, then the compressive force of the water will cause the aluminum to be compressed to some degree. As the molecules of aluminum get closer together, the repulsive force between them would be increased, until the outer force and inner force reached equilibrium.

That's how it seems to me.There must be tables somewhere of the compressive strength of aluminum - the number of pounds per sq. in. (or Newtons per sq. cm.) it takes to deform it. You could also calculate the pressure at various depths, say at the bottom of the Marianas Trench, which is around 30,000 below sea level.
You might be able to compress the aluminium very very slightly I suppose. However I think the temperature difference down there is likely to have a bigger effect on the volume of the cube than the pressure.
Hard to say. I'm sure there are tables of the water temperature at various depths. I don't believe it's too much below 0° C.
 
  • #5
CWatters
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Not necessarily. If the pressure exerted by the water is greater than the repulsive force of the aluminum molecules, then the compressive force of the water will cause the aluminum to be compressed to some degree. As the molecules of aluminum get closer together, the repulsive force between them would be increased, until the outer force and inner force reached equilibrium.

That's what I meant. Sorry if not clear.
 
  • #6
CWatters
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So the cold temperature prevents changes in volume?

No, what I meant was the block might "shrink" more due to the lower temperature than due to the increased pressure. However I haven't looked for the figures for aluminium.
 

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