एक खोखले गोलीय कोश की आंतरिक और बाह्य त्रिज्या क्रमशः 4 सेमी और 8 सेमी है। इसे पिघलाकर \(9 \frac{1}{3}\) सेमी ऊँचाई वाले एक ठोस लंब वृत्तीय बेलन में ढाला जाता है। बेलन का वक्र पृष्ठीय क्षेत्रफल (सेमी2 में) क्या है?

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AAI Junior Assistant (Fire Service) Official Paper (Held On: 15 Nov, 2022 Shift 2)
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  1. \(\frac{448}{3}\) π
  2. \(\frac{896}{3}\) π
  3. 168 π
  4. 112 π

Answer (Detailed Solution Below)

Option 1 : \(\frac{448}{3}\) π
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दिया गया है:

खोखला गोलीय कोश:

आंतरिक त्रिज्या (r1) = 4 सेमी

बाह्य त्रिज्या (r2) = 8 सेमी

बेलन:

ऊँचाई (h) = 9 (1/3) सेमी = 28/3 सेमी

प्रयुक्त सूत्र:

खोखले गोले का आयतन = (4/3)π(r23 - r13)

बेलन का आयतन = πr2h

बेलन का वक्र पृष्ठीय क्षेत्रफल = 2πrh

परिकलन:

खोखले गोलीय कोश का आयतन:

Vs = (4/3)π(83 - 43)

(4/3)π(512 - 64) = (4/3)π(448)

Vs = (1792/3)π सेमी3

बेलन का आयतन = खोखले गोले का आयतन:

πr2h = (1792/3)π = r2(28/3) = 1792/3

r2 = 1792 / 28 = 64

r = 8 सेमी

बेलन का वक्र पृष्ठीय क्षेत्रफल = 2πrh

2π(8)(28/3)

वक्र पृष्ठीय क्षेत्रफल = 448π/3 सेमी2

बेलन का वक्र पृष्ठीय क्षेत्रफल \(\frac{448}{3}\)π सेमी2 है।

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