Change in length $(\delta l)=\frac{P*L}{AE}$

Given, $P=130*10^3 N, L=4200mm$

$W=35mm, t=25mm$

$E=200GPa, E=200*10^3 N/mm^2$

$\mu=0.3$

$\delta L=\frac{130*10^3*4200}{35*25*4200)10^3}$

$\delta L=1.48mm$

$Poisson's Ratio=\frac{Lateral strain}{Longitudinal strain}$

**Calculations of changes in width : -**

$Lateral strain=\frac{\delta w}{w} or \frac{\delta t}{t}$

$Longitudinal strain=\frac{\delta L}{L}$

$\mu=\frac{\frac{\delta w}{w}}{\frac{\delta L}{L}}$

$0.3=\frac{\frac{\delta w}{35}}{\frac{2}{4200}}$

$\delta W=0.022mm$

Calculation of change in thickness:

$\mu=\frac{\frac{\delta t}{t}}{\frac{\delta L}{L}}$

$0.3=\frac{\frac{\delta t}{25}}{\frac{2}{4200}}$

$\delta t=0.015mm$