Question

If $1c{m}^2$ of cost iron weight 21 g. find the weight of a cast iron pipe of length 1 m with a bore of radius 3 cm in which the thickness of the metal is 1 cm.

Answer 1

Volume= $\pi \times l(R^2-r^2)$

where R is the outer radius which is 3+1= 4 cm

r= inner radius= 3cm

V=$\pi \times 100(4^2-3^2)$

$\Rightarrow 2198c{m}^3$

weight =$volume\times density$

density = $21gm/c{m}^3$

$\therefore weight=2198c{m}^3\times 21gm/c{m}^3=46158gm=46.158kg$