Chapter 9. Hooke's law for an object under tension or compression (9-3)

Question

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{"title":"Tensile or compressive stress on the object: applied force divided by the object’s cross-sectional area","description":"Correct!","type":"correct","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"2,3,59,122\"}]"} {"title":"Young’s modulus tells you how stiff the material is of which the object is made: Larger value means stiffer.","description":"Wrong","type":"incorrect","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"118,11,119,13\"},{\"shape\":\"rect\",\"coords\":\"137,35,173,85\"},{\"shape\":\"rect\",\"coords\":\"154,37,157,37\"}]"} {"title":"Tensile or compressive strain of the object: resulting change in length divided by the object’s relaxed length","description":"Incorrect","type":"incorrect","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"220,10,254,55\"}]"}

Question

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{"title":"Tensile or compressive stress on the object: applied force divided by the object’s cross-sectional area","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"2,3,59,122\"}]"} {"title":"Young’s modulus tells you how stiff the material is of which the object is made: Larger value means stiffer.","description":"Correct!","type":"correct","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"118,11,119,13\"},{\"shape\":\"rect\",\"coords\":\"137,35,173,85\"},{\"shape\":\"rect\",\"coords\":\"154,37,157,37\"}]"} {"title":"Tensile or compressive strain of the object: resulting change in length divided by the object’s relaxed length","description":"Incorrect","type":"incorrect","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"220,10,254,55\"}]"}

Question

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{"title":"Tensile or compressive stress on the object: applied force divided by the object’s cross-sectional area","description":"Wrong","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"2,3,59,122\"}]"} {"title":"Young’s modulus tells you how stiff the material is of which the object is made: Larger value means stiffer.","description":"Incorrect","type":"incorrect","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"118,11,119,13\"},{\"shape\":\"rect\",\"coords\":\"137,35,173,85\"},{\"shape\":\"rect\",\"coords\":\"154,37,157,37\"}]"} {"title":"Tensile or compressive strain of the object: resulting change in length divided by the object’s relaxed length","description":"Correct!","type":"correct","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"220,10,254,55\"}]"}

Review

Here’s a useful way to rewrite Hooke’s law for an object under tension or compression. This will also help us define \(\textit{stress}\) and \(\textit{strain}\) more precisely. First we substitute \(k\) from Equation 9-2 into Equation 9-1.

\(F = \left(Y\frac{A}{L_0}\right)\Delta{L}\)

Then we divide both sides by the cross-sectional area A: