Question

A $10cm$ long needle can just rest on the surface of water without wetting, its weight is :

• A. $0.014N$
• B. $0.14N$
• C. $1.4N$
• D. $14N$

Answer 1

The correct option is A $0.014N$

Surface Tension of Water $\left(T\right)=0.00072N/cm$

Here, Weight = Surface tension force = $2Tl$

$\Rightarrow Weight=2\times 0.00072\times 10=0.014N$

Therefore, A is correct option.