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A hollow iron pipe is 21 cm long and its exterior diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weighs 8 g/cm³, then the weight of the pipe is (Take π = 22/7)
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- 3.696 kg
- 3.6 kg
- 36 kg
- 36.9 kg
- 3.696 kg
Correct Option: A
The pipe can be assumed as hollow cylinder.
| External radius = | = 4 cm. | |
| 2 |
Thickness = 1 cm
∴ Internal radius = 4 – 1 = 3 cm.
Volume of the material = π h (R2 – r2)
| = | × 21 × (4² - 3²) | |
| 7 |
| = | × 21 × 7 = 462 cm³ | |
| 7 |
Now, 1cm3 iron weighs = 8 gm
∴ 462 cm³ iron weighs
= 462 × 8 gm
| = | kg | |
| 1000 |
= 3.696 kg
