Chapter 7: Problem 898
A \(5 \mathrm{~m}\) long aluminum wire $\left[\mathrm{Y}=7 \times 10^{10}\left(\mathrm{~N} / \mathrm{m}^{2}\right)\right]\( of diameter \)3 \mathrm{~mm}\( supports a \)40 \mathrm{~kg}$ mass. In order to have the same elongation in a copper wire $\mathrm{Y}=12 \times 10^{10}\left(\mathrm{~N} / \mathrm{m}^{2}\right)$ of the same length under the same weight, the diameter should now be in \(m m \ldots \ldots \ldots \ldots\) (A) \(1.75\) (B) \(1.5\) (C) \(2.5\) (D) \(5.0\)