r వ్యాసార్థం ఉండే ఒక లోహపు అర్థ గోళాన్ని కరిగించి భూమి = r ఉన్న లంబకోణ వృత్తాకార శంఖువులోకి పోతపోయటం జరుగుతుంది. వాటి వక్రతల వైశాల్యాల నిష్పత్తి ఎంత?

This question was previously asked in
RRC Group D Previous Paper 19 (Held On: 10 Dec 2018 Shift 2)
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  1. 5/√2
  2. 2/√5
  3. 3/2
  4. 5/2

Answer (Detailed Solution Below)

Option 2 : 2/√5
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Detailed Solution

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మనకి తెలిసినట్టు,

అర్థగోళపు ఘనపరిమాణం = (2/3)πr3

శంఖువు ఘనపరిమాణం = (1/3)πr2h

ప్రశ్న ప్రకారం

(1/3)πr2h = (2/3)πr3

h = 2r

మనకి తెలిసినట్లు,

l2 = r2 + h2

⇒ l2 = r2 + (2r)2

⇒ l2 = 5r2

⇒ l = √5 r

అర్ధగోళపు వక్రతల వైశాల్యం = 2πr2

శంఖువు యొక్క వక్రతల వైశాల్యం = πrl = πr × (√5r) = √5r2

కావాల్సిన నిష్పత్తి = 2πr2/√5πr2 = 2/√5
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