The lower end of a capillary tube is dipped into water and it is observed that the water in capillary tube rises by 7 . 5 cm . Find the radius of the capillary tube used, if surface tension of water is 7 . 5 × 10 - 2 N m - 1 ? Angle of contact between water and glass is 0 ° and acceleration due to gravity is 10 m s - 2 .

Step-by-step solution

Height of rise of liquid due to surface tension in a capillary tube, h = 2 S cos θ r ρ g Given that, height of liquid rise h = 7 . 5   cm ,   surface tension of water S = 7 . 5 × 10 - 2   N   m - 1   and the angle of contact between water and glass is θ = 0 ° h = 2 S cos θ r ρ g ⇒ r = 2 S cos θ h ρ g = 2 7 . 5 × 10 - 2   N   m - 1 cos 0 °   7 . 5 × 10 - 2   m 1000   kg   m - 3 10   m