Question 92: Properties of Matter

Question

If 1000 droplets of water of surface tension $$0.07 \mathrm{~N} / \mathrm{m}$$, having same radius $$1 \mathrm{~mm}$$ each, combine to from a single drop. In the process the released surface energy is :-
$$\left( {\mathrm{Take}\,\pi  = {{22} \over 7}} \right)$$

Accepted Answer

$1000 	imes \frac{4 \pi}{3}(1)^{3}=\frac{4 \pi}{3} \mathrm{R}^{3}$
$\mathrm{R}=10 \mathrm{~mm}$
$\mathrm{T} 	imes 1000 	imes 4 \pi\left(10^{-3}ight)^{2}-\mathrm{T} 	imes 4 \pi\left(10 	imes 10^{-3}ight)^{2}=\Delta \mathrm{E}$
$$ \Rightarrow $$ $\Delta \mathrm{E}=4 	imes \pi 	imes 7 	imes 10^{-2}[1000-100] 	imes 10^{-6}$
$$ \Rightarrow $$ $\Delta \mathrm{E}=7.92 	imes 10^{-4} \mathrm{~J}$

Answer

$$7 .92 	imes 10^{-4} \mathrm{~J}$$

Answer

$$7 .92 	imes 10^{-6} \mathrm{~J}$$

Answer

$$8 .8 	imes 10^{-5} \mathrm{~J}$$

Answer

$$9 .68 	imes 10^{-4} \mathrm{~J}$$

Properties of Matter

If 1000 droplets of water of surface tension $0.07 \mathrm{~N} / \mathrm{m}, having same radius 1 \mathrm{~mm} each, combine to from a single drop. In the process the released surface energy is :- \left( {\mathrm{Take}\,\pi = {{22} \over 7}} \right)

Choose the correct answer: