Question

The surface tension of a liquid in CGS system is $45dynec{m}^{-1}$. Its value in SI system is:

• A. $4.5{Nm}^{-1}$
• B. $0.045{Nm}^{-1}$
• C. $0.0045{Nm}^{-1}$
• D. $0.45{Nm}^{-1}$

Answer 1

The correct option is B $0.045{Nm}^{-1}$

$1dyne={10}^{-5}N$
$1cm={10}^{-2}m$

$\therefore \frac{dyne}{cm}=\frac{{10}^{-5}N}{{10}^{-2}m}=\frac{{10}^{-3}N}{m}$

$\therefore \frac{45dyne}{cm}=\frac{45\times {10}^{-3}N}{m}=0.045N/m$