The surface tension of a liquid is 70 dyne/cm . . .

Question : The surface tension of a liquid is 70 dyne/cm. In MKS system its value is?

a) 70 N/m
b) 7×10-2 N/m
c) 7×102 N/m
d) 7×103 N/m

Doubt by Jaskirat

Solution : 

We can do this question by long method but still we don't do it by that because it's a 1 Mark MCQ question. So we will do it by short method. 

One thing is clear that we have to convert the units from dyne/cm (CGS) to Newton/m (MKS)

We know, 
1 N = 105 dynes
⇒ 1 dyne = (1/105) N or 10-5 N

1 m = 100 cm 
⇒ 1 cm = (1/100) m or 10-2 m

So
70 dyne/cm
= 70 [10-5 N]/[10-2 m]
= (70×10-5)/(10-2) N/m
= 7×10-2 N/m

Hence, b) would be the correct option.