question_answer

The maximum force, in addition to the weight required to pull a wire of 5.0 cm long from the surface of water at temperature \[20{}^\circ C\]is 728 dynes. The surface tension of water is

A) \[7.28\,N/cm\]  

B) \[7.28\,dyne/cm\]

C) \[72.8\,dyne/cm\]

D) \[7.28\times {{10}^{2}}\,dyne/cm\]

Correct Answer: C

Solution :

[c] \[T=\frac{F}{2l}=\frac{728}{2\times 5}\] \[\therefore T=72.8dyne/cm\]