JEE Main 2025 Physics question
A capillary tube of radius 0.1 mm is partly dipped in water (surface tension 70 dyn/cm and glass water contact angle ≈ 0°) with 30° inclined with the vertical. The length of water risen in the capillary is cm. (Take g = 9.8 m/s²)
Answer: (1)
Solution
h = 2Tcosθ/(ρgr) = 100/7 cm (vertical rise); length along tube = h/cos30° ≈ 200/(7√3) ≈ 16.49 ≈ 82/5.