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QJEEM20Phb3ca: JEE Main 2020 Physics - Class 11 JEEM20Phb3ca Solution: When a long glass capillary tube of radius 0.015 cm is dipped…

When a long glass capillary tube of radius 0.015 cm is dipped in a liquid, the liquid rises to a height of 15 cm within it. If the contact angle between the liquid and glass to close to 0o, the surface tension of the liquid, in milliNewton m–1, is [ρ(liquid) = 900 kgm–3, g = 10 ms–2]
(Give answer in closest integer) _____.

Step-by-Step Verified Solution

Capillary rise

h = 2Tcos⁡θρgr

⇒ T = ρgrh2cos⁡θ

= (900)(10)(15×10−5)(15×10−2)2

= 1012.5 × 10–4

= 101.25 × 10–3 = 101.25 mN/m

≃ 101.00 mN/m

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