How strong is Superman?

  • #1

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[Moderator's note: Unnecessary introductory statement deleted.]

There's a comic where Superman breaks out/shatters chains that were designed to haul stars across the galaxy
- Let's say these chains were made to pull (our) sun
What tensile strength would a chain need to help pull our sun without breaking? And if I'm not asking the right questions, please let me know what other information you need to solve this
inCollage_20200421_172250667.jpg
 
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  • #2
phinds
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What tensile strength would a chain need to help pull our sun without breaking?
Forgetting the absurdity of the scenario, it is an incomplete problem statement. Do you understand what's missing?
 
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  • #3
Forgetting the absurdity of the scenario, it is an incomplete problem statement. Do you understand what's missing?
I do not know what's missing. Enlighten me
 
  • #4
256bits
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I do not know what's missing. Enlighten me
Do you need a half inch diameter rope to pull a bus, or a 10 inch thick rope?
 
  • #5
phinds
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Do you need a half inch diameter rope to pull a bus, or a 10 inch thick rope?
And that would still leave something missing. Think classical mechanics 101.

EDIT: ah, wait. I see now. I was thinking of how fast you accelerate it but that is NOT really the question.
 
  • #6
256bits
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And that would still leave something missing. Think classical mechanics 101.
It is a hint to help figure out what is missing.
 
  • #7
Do you need a half inch diameter rope to pull a bus, or a 10 inch thick rope?
Ah, I see what you mean. Not really sure for this one though. Diameter doesn't look that big compared to his arm
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  • #8
phinds
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It is a hint to help figure out what is missing.
Yes. I edited my post before your post appeared.
 
  • #9
I'm just randomly guessing here, but, is the force of the pull needed as well?
 
  • #10
phinds
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Ah, I see what you mean. Not really sure for this one though. Diameter doesn't look that big compared to his arm
Irrelevant. The question is not about THAT chain because it is already stated to be unbreakable (absurd because that implies infinite tensile strength). You are asking about a breakable chain, else the question doesn't even make sense.
 
  • #11
Irrelevant. The question is not about THAT chain because it is already stated to be unbreakable (absurd because that implies infinite tensile strength). You are asking about a breakable chain, else the question doesn't even make sense.
Don't mind the unbreakable statement, it's just hyperbole
 
  • #12
phinds
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Don't mind the unbreakable statement, it's just hyperbole
Exactly what I just said, as regards your question.
 
  • #13
256bits
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And that would still leave something missing. Think classical mechanics 101.

EDIT: ah, wait. I see now. I was thinking of how fast you accelerate it but that is NOT really the question.
OK , Now you got me..
 
  • #14
Exactly what I just said, as regards your question.
Right, so I just need the diameter of said chain? Let's assume it's 4 inches. What's my next step?
 
  • #15
phinds
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OK , Now you got me..
Well, if you wanted to get it moving from zero to a zillion miles and hour in 6 seconds (relative to its starting position), you'd need a different tensile strength than if you wanted to just barely move it. Minimum tensile strength in this situation means just barely getting the sun moving before the chain breaks. He HAS to be asking about minimum tensile strength, else the question would have no answer.
 
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  • #16
Well, if you wanted to get it moving from zero to a zillion miles and hour in 6 seconds (relative to its starting position), you'd need a different tensile strength than if you wanted to just barely move it. Minimum tensile strength in this situation means just barely getting the sun moving before the chain breaks. He HAS to be asking about minimum tensile strength, else the question would have no answer.
yes, minimum tensile strength.
And let's assume it's moving from 0 to 184,410 miles per second in 1 minute

Thanks by the way. At first I didn't know what's needed to continue
 
  • #17
So a 4 inch diameter chain, wrapped around our sun. Being pulled, moving the sun, going from 0 to 184,410 miles per second in 1 minute

How tough would that chain need to be?
 
  • #18
phinds
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So a 4 inch diameter chain, wrapped around our sun. Being pulled, moving the sun, going from 0 to 184,410 miles per second in 1 minute
No, with that question you are NOT trying for minimum tensile strength but some specific tensile strength greater than the minimum. Reread post #15
 
  • #19
No, with that question you are NOT trying for minimum tensile strength but some specific tensile strength greater than the minimum. Reread post #15
Oh ok I understand what you were saying now 👍
 
  • #20
phinds
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So a 4 inch diameter chain, wrapped around our sun. Being pulled, moving the sun, going from 0 to 184,410 miles per second in 1 minute

How tough would that chain need to be?
Another point to be made here is that you are specifying zero to almost the speed of light in 1 minute. That would require something ENORMOUSLY beyond the maximum possible tensile strength (the point where molecular bonds can't hold).
 
  • #21
Another point to be made here is that you are specifying zero to almost the speed of light in 1 minute. That would require something ENORMOUSLY beyond the maximum possible tensile strength (the point where molecular bonds can't hold).
Right, it's not realistically possibleI know. Good thing this is the science fiction section of this website

Is there a formula(s) I can use to help figure this out?
 
  • #22
phinds
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How would I find out the tensile strength needed for a chain to pull our star from 0 to 184,410 miles per second in one minute?
Another way to view this question is that it is exactly equivalent to: "if the laws of physics no longer apply, what do those laws say about <insert statement of your choice>.
 
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  • #23
PeterDonis
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What tensile strength would a chain need to help pull our sun without breaking?
You can't pull our Sun. It's not solid and will not move as a single coherent object if a force is applied to it.

The best you can do is to do the computation for some hypothetical object with the mass of our Sun that will move as a single coherent object when subjected to the large acceleration required by your specifications. See below.

let's assume it's moving from 0 to 184,410 miles per second in 1 minute
This is 0 to 0.98995 c in 60 seconds, which works out to an acceleration of 504,727 g. (You should be able to verify this computation.)

Is there a formula(s) I can use to help figure this out?
Once you have the acceleration, you know the force required to impose that acceleration on an object with the mass of the Sun. Then you can just use standard formulas for the breaking strength of a cable to find what tensile strength would be required for a cable of your given cross sectional area to sustain that force.
 
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  • #24
PeterDonis
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Another way to view this question is that it is exactly equivalent to: "if the laws of physics no longer apply, what do those laws say about <insert statement of your choice>.
This response is not quite justified. There is a valid objection to be made about trying to pull our actual Sun with a cable (which I made in my post in response to the OP just now), but there is also a valid calculation that can be made within the known laws of physics for a hypothetical object with the mass of our Sun subjected to the specified acceleration (which I described in my post in response to the OP just now).

The result of that calculation (which I'll let the OP discover for himself) does not actually give a tensile strength that violates the known laws of physics--it still implies a sound speed in the material that is less than the speed of light. (You actually don't have to do the full calculation I described to see this--you can combine the acceleration I gave with the known diameter of the Sun to check that my statement is correct. Can you see how?)
 
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  • #25
PeterDonis
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All thread participants, please note, some inappropriate posts have been deleted. Please be civil to other posters. Thanks!
 
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