Q15 of 189 Page 492

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.

Given,


Weight of 1 cm3 cast iron = 21 g


Length of wire = h = 1 m = 100 cm


Internal radius (r1) =


Thickness of metal = 1 cm


So, External radius (r2) = 1.5 + 1 = 2.5 cm


Volume of metal = (External volume – internal volume)


= πr22h – πr12h = πh (r22 – r12) = × 100 (2.5 + 1.5) (2.5 – 1.5)


= × 100 × 4 × 1 cm3


Weight of metal =


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