Question

If value of surface tension of a liquid is $70$ dyne/cm, then its value in $N / m$ will be

• A. $7 \times 10^{3} N / m$
• B. $ 7\times 10^{2}N/m $
• C. $ 7\times 10^{-2}N/m $
• D. $ 70\,N/m $

Answer 1

Answer: (C)

The unit dyne/cm is $CGS$ system of unit.
The $CGS$ unit of force is dyne and SI unit is Newton.
Also there are $10^{5}$ dynes in one newton and $100\, cm$ in $1\, cm$.
$\therefore \frac{70 \text { dynes }}{ cm }=\frac{70 \times 10^{-5}}{10^{-2}}$
$=7 \times 10^{-2} \,N / m$