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A wire of length \mathrm{L}$ and radius $\mathrm{r} is clamped rigidly at one end. When the other end of the wire is pulled by a force \mathrm{F}, its length increases by 5 \mathrm{~cm}. Another wire of the same material of length 4 \mathrm{~L} and radius 4 \mathrm{r} is pulled by a force 4 \mathrm{~F} under same conditions. The increase in length of this wire is ____________\mathrm{cm}.

Option: 1

5


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

For the same material young's modules \mathrm{(Y)} will be same

\mathrm{\because Y= \frac{F}{A} \times \frac{l}{\Delta l} }

\mathrm{\therefore \frac{F_1}{\pi r^2} \times \frac{l}{\Delta l_1}=\frac{F_2}{\pi(4r)^2} \times \frac{4 l}{\Delta l_2} }

\mathrm{\frac{\Delta l_{1}}{\Delta l_{2}}=\frac{F_{1}}{F_{2}}\times \frac{16r^{2}}{l\left ( r^{2} \right )}\times \frac{l}{4l}}

\mathrm{\frac{\Delta l_1}{\Delta l_2} =1 }

\mathrm{\Delta l_2 =\Delta l_1=5 \mathrm{~cm}}

The increase in the length of wire of length \mathrm{4L} is \mathrm{5\: \: cm}

Posted by

Rakesh

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