If the excess pressure inside a soap bubble of radius 5mm is equal to the pressure of a water column of height 0.8cm, then what is the surface tension of the soap solution.

Explanation

Excess pressure = 4T/R and hydrostate pressure = `hrhog`
`therefore 4T/R = `hrhog`
`therefore T = (hrhogR)/4`
= `(8 xx 10^-3 xx 10^3 xx 98 xx 5 xx 10^-3)/4 = 9.8 xx 10^-3 N/m`