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The diameter and height of a cylinder are measured by a meter scale to be 12.6 ± 0.1 cm and 34.2 ± 0.1 cm, respectively. What will be the value of its volume in appropriate significant figures?1. 4300 ± 80 cm32. 4260 ± 80 cm33. 4264.4 ± 81.0 cm34. 4264 ± 81 cm3 |
Answer» Correct Answer - Option 2 : 4260 ± 80 cm3 Concept: Volume of a cylinder of radius ‘r’ and height h is given by V = πr2 h Or \(V = \pi {\left( {\frac{D}{2}} \right)^2}h\) \(\left[\because {d = 2r \Rightarrow r = \frac{d}{2}} \right]\) \(V = \frac{1}{4}\left( {\pi {D^2}h} \right)\) Where D is the diameter of circular surface Calculation: Given, Diameter of the cylinder, D = 12.6 ± 0.1 cm Height of the cylinder, h = 34.2 ± 0.1 cm Here, D = 12.6 cm and h = 34.2 cm \(V = \frac{\pi }{4} \times {\left( {12.6} \right)^2} \times \left( {34.2} \right)\) \(V = \frac{\pi }{4} \times 158.76 \times 34.2\) \(V = \frac{\pi }{4} \times 5429.592\) V = 1357.398 × π V = 1357.398 × 3.14 V = 4262.22 cm3 V = 4260 (in three significant numbers) We know that, ΔD = ± 0.1 and Δh = ± 0.1 Now, error calculation can be done as \(\frac{{{\rm{\;\Delta }}V}}{V} = 2\left( {\frac{{{\rm{\Delta }}D}}{D}} \right) + \frac{{{\rm{\Delta }}h}}{h} = \frac{{2 \times 0.1}}{{12.6}} + \frac{{0.1}}{{34.2}}\) \(\frac{{{\rm{\Delta }}V}}{V} = 0.0158 + 0.0029\) \(\frac{{{\rm{\Delta }}V}}{V} = 0.01879\) ΔV = (0.01879) × (4262.22) ΔV = 79.7 ≈ 80 cm3 ∴ For proper significant numbers, volume reading will be V = 4260 ± 80 cm3 Therefore, the value of its volume in appropriate significant figures is 4260 ± 80 cm3 |
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