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A cylindrical roller made or iron is 1.2 m long. Its internal radius is 24 cm and thickness of the iron sheet used in making the roller is 15 cm. What is the mass (in kg) of the roller, if 1 cm3 of iron has 8 g mass?1. 892.8 π 2. 907.2 π3. 846.72 π4. 845.75 π |
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Answer» Correct Answer - Option 2 : 907.2 π Given: Length of the roller is 1.2 m. Its internal radius is 24 cm and thickness is 15 cm. 1 cm3 of iron has 8 g mass Concept Used: If R be the external radius and r be the internal radius and h be the height of a cylinder then the volume of the material of the cylinder is π(R2 - r2)h Calculation: Length of the roller (h) = 1.2 m = 120 cm The internal radius of the cylinder (r) = 24 cm The thickness of the cylinder is 15 cm External radius of the cylinder (R) = (24 + 15) = 39 cm The volume of the cylinder is π(392 - 242) × 120 ⇒ 113400π cm3 Mass of 1 cm3 iron is 8 g Mass of 113400π cm3 iron is (113400π × 8) g ⇒ 907200π g ⇒ 907.2π kg [∵ 1 kg = 1000 g] ∴ The mass of the roller is 907.2π kg. |
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