JEE Main Online Paper (Held On 09 April 2013)
A) \[\frac{3c}{2a{{b}^{2}}}\]
B) \[\frac{2{{a}^{2}}c}{b}\]
C) \[\frac{3a}{2{{b}^{2}}c}\]
D) \[\frac{2ac}{{{b}^{2}}}\]
Correct Answer: C
Solution :
For steel wire As change in length \[(\Delta {{l}_{1}})=\frac{3Mg{{l}_{1}}}{r_{1}^{2}\pi {{y}_{1}}}\] ...(i) and for beam wire, Change in length \[(\Delta {{l}_{2}})=\frac{2Mg\,{{l}_{2}}}{\pi r_{2}^{2}{{y}_{2}}}\] ...(ii) Dividing Eq. (i) by (ii), we get, r Corresponding ratio of increase in their lengths \[=\frac{3a}{2{{b}^{2}}c}\]
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