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    				| 1. | A copper wire of cross sectional asrea 0.01 cm is under a tension of 20 N. Find the decrease in the cross sectional area. Young modulus of copper `=1.1xx10^11Nm^-2` and Poisson ratio 0.32. | 
| Answer» Correct Answer - A::B::C::D `A=0.01 cm^2` `=10^-6m^2` `=T=20N` `Y=1.1xx10^11N/m^2` we know that `Y=(FL)/(A/_\\L)` `=(/_\\L)/L=F/(AY)` `=20/(10^-6xx1.1x10^11)x18.18xx10^-5` `d=((/_\\D)/D)/((/_\\L)/L)=0.32` `So, (/_\\D)/D=(0.32)xx(KL)/L` `=32xx(18.18)xx10^5=5.81xx10^-5` Again `(/_\A)/A=(2/_\\r)/r` `rarr /_\\A=(2/_\\r)/r` `/_\\A=2xx(5.8xx10^-5)xx(0.01)` `=1.16xx10^9N/m^2` | |