A wire with diameter $d$ and length $l$ is suspended vertically from a fixed support. By attaching a mass $M$ to its lower end, the wire is stretched. The Young modulus of the wire is $E$. The acceleration of free fall is $g$. Which equation is used to find the extension $x$ of the wire?
- A$x = \dfrac{Ml}{\pi d^2 E}$
- B$x = \dfrac{Mgl}{\pi d^2 E}$
- C$x = \dfrac{4Mgl}{\pi d E}$
- D$x = \dfrac{4Mgl}{\pi d^2 E}$