Surface Tension

(1) $T = F/l (={dw}/{dA})$

(2) When n drops (each of radius r) coalesce into a single drop of radius R, or a single drop of radius R breaks into n drops.
$R^3 = n r^3$

Energy released/absorbed = $4 π T = (n r^2 – R^2)$

(3) For a drop, $P_i – P_o = {2T}/{r}$

(4) For a bubble, $P_i – P_o = {4T}/{r}$

(5) 2T cosθ = h r ρ g

(6) $T = T_o (1 – αθ)$ θ -> change in temperature

(7) $h_1 r_1 = h_2 r_2$