Does a cube of aluminum yield in the sea?

AI Thread Summary
A cube of aluminum suspended deep in the ocean may experience some compression due to increased water pressure at greater depths, but the internal pressure remains equal to the external pressure. The temperature at depth could significantly affect the cube's volume, potentially causing it to "shrink" more than pressure alone would. There is a discussion about the balance between compressive forces from water and repulsive forces from aluminum molecules, suggesting that deformation is possible but minimal. Calculating the pressure at various ocean depths, such as the Marianas Trench, could provide more insight into the compressive strength of aluminum. Overall, both pressure and temperature play crucial roles in determining whether the aluminum cube will yield.
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?


Homework Equations





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.
 
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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.
 
So the cold temperature prevents changes in volume?
I did not think about that.
Thanks,
Ryan.
 
CWatters said:
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.
CWatters said:
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.
 
Mark44 said:
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.
 
hermtm2 said:
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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