ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: Akirus on June 06, 2010, 03:04:25 pm
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Few solutions in materials and structures detailed study that I disagree with, someone prove me wrong:
1. Which of the following means that copper has a tensile strength of 2.5 * 10^8 Nm^-2?
Solution says B: "A sample will become permanently deformed if subjected to a stress greater than 2.5 * 10^8 Nm^2". Doesn't that describe the elastic limit?
I selected A: "A sample of copper will probably break if subjected to a stress of 2.5 * 10^8 Nm^-2", which falls more in line with the definition of 'strength'.
3. You'd have to look at the diagram for this question, it's a graph. None of the curves have a clearly marked breaking point, so I selected D (i.e. impossible to tell as maximum tensile strength is unknown); for all we know, isoprene may break where it is whereas neoprene and urethane could extend a lot further.
4. If neoprene is stretched 7 times its original length, then change in length = 6l (since 1l + 6l = 7l) => strain = 6l/l = 6. I don't see how it could be 7.
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Tensile strength is the maximum stress the sample withstands, ie. the maximum on the stress-strain curve. B is the yield strength. A seems more correct here.
With 4 it says that it stretched 7 times its length, this is the length of the actual stretch ie. the entire length is now 8l. It was not stretched to 7 times its length.
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Encountered the same problem with question one:
Tensile strength - the force required to pull something such as rope, wire, or a structural beam to the point where it breaks.
Yield strength - The stress a material can withstand without permanent deformation.
Aremy definitions wrong?
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Sorry i still don get q 4...once u get the change in L then what?how to fin the stress? Youngs modulus =stress/strain?
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Read it of the graph! The y-axis represent the stress.
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Tensile strength is the maximum stress the sample withstands, ie. the maximum on the stress-strain curve. B is the yield strength. A seems more correct here.
With 4 it says that it stretched 7 times its length, this is the length of the actual stretch ie. the entire length is now 8l. It was not stretched to 7 times its length.
"Neoprene is stretched to 7 times its original length."
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Read it of the graph! The y-axis represent the stress.
LOL thanks :P hahaha i cant belive i asked that question
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Tensile strength is the maximum stress the sample withstands, ie. the maximum on the stress-strain curve. B is the yield strength. A seems more correct here.
With 4 it says that it stretched 7 times its length, this is the length of the actual stretch ie. the entire length is now 8l. It was not stretched to 7 times its length.
"Neoprene is stretched to 7 times its original length."
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Ok, then you're right.