A bubble having surface tension T and radius R is formed on a ring of radius b `(b lt gt R)` . Air is blown inside the tube held in front of the ring , with velocity `upsilon` as shown in fig. The air molecules collides perpendicularly with the wall of the bubble and stops. Calculate the radius R at which the bubble and stops. Calculate the radius R at which the bubble separates from the ring.

Explanation

The various force acting on the ring are shown in fig. The bubble will separted from the ring when rate fo chage of momentum of air falling on the wall of the bubble is equal to the force of surface tension acting on the surface of bubble incontact with the ring. i.e
`rho A upsilon^(2) = 2 pi b 2 T sin theta = 4 pi b T xx b/R`
or ` rho pi b^(2) upsilon^(2) = 4 pi T b^(2)//R or R = (4t)/(rho upsilon^(2))`.