Question

If 1 cm³ of cast iron weighs 21g, find the weight of a cast iron pipe of length 1m with a bore of 3cm in which the thickness of the metal is 1cm.

Answer 1

We know that

Internal radius = 3/2 = 1.5cm

External radius = 1.5 + 1 = 2.5cm

We know that

Volume of cast iron = (π × (2.5)² × 100 – π × (1.5)² × 100)

Taking the common terms out

Volume of cast iron = π × 100 × (2.5² – 1.5²)

On further calculation

Volume of cast iron = (22/7) × 100 × (6.25 – 2.25)

So we get

Volume of cast iron = (22/7) × 100 × 4 = 1257.142 cm³

It is given that 1cm³ of cast iron weighs 21g

We know that 1kg = 1000g

So the weight of cast iron pipe = 1257.142 × (21/1000) = 26.4kg

Therefore, the weight of cast iron pipe is 26.4 kg.