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Topic: what's the new density? (Read 1569 times) |
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Marissa
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what's the new density?
« on: May 2nd, 2008, 1:15pm » |
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Suppose you have a long cylinder has internal and external radius, R1 and R2 respectively. It is made of an elastic material with density p.
The cylinder is then loaded such that the internal and external pressures are maintained at P. What is the new density of the deformed cylinder material?
And, suppose that hollow cylinder contains a gas at an internal pressure of P. The external pressure (outside the cylinder) is also maintained at P.
What is the maximum stress occuring in the cylinder material?
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| « Last Edit: May 2nd, 2008, 1:23pm by Marissa » |
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temporary
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Re: what's the new density?
« Reply #1 on: May 11th, 2008, 9:52am » |
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Pressurizing it changes not its density, it is still the same material with the same mass and density. The density is still p.
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Benny
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Re: what's the new density?
« Reply #2 on: May 11th, 2008, 12:32pm » |
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In high school, I was told that solids (and liquids) don't compress; as opposed to a gas. But, later, when i took college physics, i learnt that solids do compress by a very small amount. This small amount is described as "bulk modulus."
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Sir Col
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Re: what's the new density?
« Reply #3 on: May 11th, 2008, 1:01pm » |
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@temporary: Density is defined as mass/volume. Change the volume of an object with fixed mass and guess what happens to its density? Admittedly the ideal gas law doesn't apply to solids, but solids under pressure will compress.
on May 11th, 2008, 12:32pm, BenVitale wrote:| In high school, I was told that solids (and liquids) don't compress... |
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temporary
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Re: what's the new density?
« Reply #4 on: May 11th, 2008, 3:48pm » |
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If the object is compressed with pressure and it changes the volume, it changes the mass also. The material is the same, so is the density. I'm not saying there is no compression, I'm saying compression isn't relevant.
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ThudnBlunder
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Re: what's the new density?
« Reply #5 on: May 11th, 2008, 4:22pm » |
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on May 11th, 2008, 3:48pm, temporary wrote:| If the object is compressed with pressure and it changes the volume, it changes the mass also. |
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Is the mass destroyed? 
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mikedagr8
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Re: what's the new density?
« Reply #6 on: May 12th, 2008, 3:12am » |
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on May 11th, 2008, 4:22pm, ThudanBlunder wrote:
Is the mass destroyed?
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Only the maths 
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Benny
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Re: what's the new density?
« Reply #7 on: May 12th, 2008, 8:23am » |
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on May 2nd, 2008, 1:15pm, Marissa wrote: ......
And, suppose that hollow cylinder contains a gas at an internal pressure of P. The external pressure (outside the cylinder) is also maintained at P.
What is the maximum stress occuring in the cylinder material?
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The maximum stress is constant and isotropic stress -- which is called pressure -- achieved everywhere, is equal to P
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JiNbOtAk
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Re: what's the new density?
« Reply #8 on: May 13th, 2008, 8:52pm » |
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on May 11th, 2008, 3:48pm, temporary wrote:| If the object is compressed with pressure and it changes the volume, it changes the mass also. |
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What ?? 
I think you mean specific density, otherwise referred to as relative density. This remains constant, as long as the reference density is the same.
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