Question

A hollow iron pipe is 10 cm long and its external diameter is 18 cm. If the thickness of the pipe is 2 cm and iron weighs 8.5 g/cm³, then the weight of the pipe from the following is closest to:
1. 8.54 kg
2. 9.54 kg
3. 7.54 kg
4. 5.54 kg

Answer 1

Correct Answer - Option 1 : 8.54 kg

Given:

External diameter = 18 cm

Thickness = 2 cm

Density = 8.5 g/cm³

Formula used:

(i) Volume = π(R2 - r2)l

(ii) Mass = Density × Volume

Calculation:

Difference between radius = thickness

⇒ R - r = 2

⇒ 9 - r = 2

⇒ r = 7 cm

Volume = π(R² - r²)l

⇒ π{(9)2 - (7)2} × 10

⇒ 320π cm³

Mass = Density × Volume

⇒ 8.5 × 320π

⇒ 2720π gm

⇒ 2.720π kg

⇒ 8.54 kg

∴ The weight of the pipe is closest to 8.54 kg.