Question

Two soap bubbles of equal radii(R=8cm) are stuck together with an intermediate film separating them.Surface tension of solution forming bubbles is 7×10^-3 N/m.What will be distance between the centres of soap bubbles

Answer 1

@sillybilly123 would you mind taking a look at this when you get a chance

Answer 2

The intermediate film will be flat with a radius of r cm.
The pressure in each soap bubble is
\[P=(4T/R) Pa\]
The force actng on the intermediate film is\[F=PA=(4T/R)*pi*r^2 \]
The force is also
\[F=(2 \pi r *T) N\]
Therefore,
\[4T/R*\pi r^2 =2 \pi rT\]
\[r=R/2\]
By Pythagoras, the distance between the centers is
\[d=2*\sqrt{(R^2-r^2)} = 2*\sqrt{(R^2-R^2/4)}=\sqrt{3}R=8*\sqrt{3}\]
\[=13.9 cm\]