Question:
A solid lead ball of radius 6 cm is melted and then drawn into a wire of diameter 0.2 cm. The length of wire is
(a) 272 m
(b) 288 m
(c) 292 m
(d) 296 m
Solution:
(b) 288 m
Let h m be the length of wire.
Volume of the lead ball = volume of the wire
$\Rightarrow \frac{4}{3} \pi \times 6^{3}=\pi \times(0.1)^{2} h$
$\Rightarrow h=\frac{4 \times 216}{3 \times 0.01}=28800 \mathrm{~cm}=288 \mathrm{~m}$