1.

One end of steel wire is fixed ti ceiling of an elevator moving up with an acceleration `2 m//s^(2)` amd a load of 10 kg hangs from other end. Area of cross- section of the wire is `2cm^(2)` .The longitudinal strain in the wire is `(g= 10 m//s^(2) and Y= 2 xx 10^(11)Nm^(2))`.A. ` 4 xx 10^(10)`B. `3 xx 10 ^(-6)`C. `8 xx 10 ^(-6)`D. ` 2 xx 10 ^(-6)`

Answer» Correct Answer - B
(b) As, `T=m(g+a_(0))=10(10+2)=120N`
Stress `=(T)/(A)=(120)/(2xx10^(4))=60xx10^(4)Nm^(-2)` and `Y=("Stress")/("Strain"), "Strain"=("Stress")/(Y)`
`=(60xx10^(4))/(2xx10^(11))`
`=30xx10^(-7)=3xx10^(-6)`


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