Discussion Forum



1)

A copper sphere of radius 3 cm is beaten and drawn into wire of diameter 0.2 cm. The length of the wire is


A) 9 m

B) 12 m

C) 18 m

D) 36 m

Answer:

Option D

Explanation:

Volume of copper sphere =$\frac{4}{3}\pi r^{3}$

=$\frac{4}{3}\pi 3^{3}$

Radius of the wire =0.1 cm

Let h be the lenght of the cylinder 

$\pi r^{2}h=36\pi$

$\pi (0.1)^{2}h=36\pi$

$h=\frac{36}{0.01}=3600 cm$

h=36 m