calcultate the force required to take away a flat plate of radius 5cm from the surface of water. Given surface tension of water=72 dyne/cm ???? (in CGS and S.I)

radius of plate = 5 cm, tension = 72 dyne/cm

force = tension * length
the plate is flat so the force due to surface tension acts on only one face
$$\begin{gathered} l=2\pi r \\ F=T\times 2\pi r \\ F=72\times 2\times 3.14\times 5=2260.8dyne \end{gathered}$$ 
1 dyne = 10^-5 newton
so 2260.8 dyne =2260.8 $\times$ 10^-5 newton