# Young's moduli of two wires A and B are in the ratio 7:4 wire. Wire A is 2 m long and has radius R. Wire B is 1.5 m long and has radius 2 mm. If the two wires stretch by the same length for a given load, then the value of R is closed to: Option 1) 1.5 mm Option 2) 1.9 mm Option 3) 1.7 mm Option 4) 1.3 mm

$Y =\frac{F\l }{\pi r^{2}\Delta \l }$

$\frac{Y_{A}}{Y _{B}}=\frac{F\l_{A}}{\pi r_{A}^{2}\Delta \l_{A}} \times \frac{\pi r_{B}^{2}\Delta \l_{B}}{F\l_{B}}$

$\frac{7}{4}=\frac{2}{\left ( r_{A} \right )^{2}} \times \frac{2^{2}}{1.5}$

$\Rightarrow r_{A}^{2}=\frac{4 \times 2 \times 2^{2}}{1.5 \times 7}$

$\Rightarrow r_{A}=1.7 mm$

Option 1)

1.5 mm

Option 2)

1.9 mm

Option 3)

1.7 mm

Option 4)

1.3 mm

### Preparation Products

##### Knockout JEE Main Sept 2020

An exhaustive E-learning program for the complete preparation of JEE Main..

₹ 12999/- ₹ 6999/-
##### Rank Booster JEE Main 2020

This course will help student to be better prepared and study in the right direction for JEE Main..

₹ 9999/- ₹ 4999/-
##### Test Series JEE Main Sept 2020

Take chapter-wise, subject-wise and Complete syllabus mock tests and get in depth analysis of your test..

₹ 4999/- ₹ 1999/-
##### Knockout JEE Main April 2021

An exhaustive E-learning program for the complete preparation of JEE Main..

₹ 22999/- ₹ 14999/-