Q. 154.4( 19 Votes )

# If of cast iron weighs 21 g, find the weight of a cast iron pipe of length 1 m with a bore of 3 cm in which the thickness of the metal is 1 cm.

Answer :

Given,

Weight of 1 cm^{3} cast iron = 21 g

Length of wire = h = 1 m = 100 cm

Internal radius (r_{1}) =

Thickness of metal = 1 cm

So, External radius (r_{2}) = 1.5 + 1 = 2.5 cm

Volume of metal = (External volume – internal volume)

= πr_{2}^{2}h – πr_{1}^{2}h = πh (r_{2}^{2} – r_{1}^{2}) = × 100 (2.5 + 1.5) (2.5 – 1.5)

= × 100 × 4 × 1 cm^{3}

Weight of metal =

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