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A solid copper cylinder of length `l=65cm` is placed on a horizontal surface and subjected to a vertical compressive force `F=1000N` directed downward and distributed uniformly over the end face. What will be the resulting change of the volume of the cylinder in cubic millimeters? |
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Answer» Volume of a solid cylinder `V=pir^2l` So, `(DeltaV)/(V)=(pi2rDeltarl)/(pir^2l)+(pir^2Deltal)/(pir^2l)=(2Deltar)/(r)+(Deltal)/(l)` (1) But longitudinal strain `Deltal//l` and accompanying lateral strain `Deltar//r` are related as `(Deltar)/(r)=-mu(Deltal)/(l)` (2) Using (2) in (1), we get: `(DeltaV)/(V)=(Deltal)/(l)(1-2mu)` (3) But `(Deltal)/(l)=(-F//pir^2)/(E)` (Because the increment in the length of cylinder `Deltal` is negative) So, `(DeltaV)/(V)=(-F)/(pir^2E)(1-2mu)` Thus, `DeltaV=(-Fl)/(E)(1-2mu)` Negative sign means that the volume of the cylinder has decreased. |
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