Question

The material of a wire has specific gravity $8$. If it is not wetted by water. what is the maximum diameter of the wire that will float on the surface of water? ($T$ $=$ $70dyne/cm$)

• A. $0.75cm$
• B. $1.5mm$
• C. $0.75m$
• D. $1.5cm$

Answer 1

The correct option is B $1.5mm$

Surface tension force $=mg$

$2Tl=\pi r^{2}l\rho g$ , $\rho =8$ ,$g=980$

we get $r=0.075cm$

so $D=2r=1.5mm$