Question

The surface energy of a liquid drop is $E$. It is sprayed into $1000$ equal droplets. The work done in spraying is

• A. $999E$
• B. $99E$
• C. $9E$
• D. $E$

Answer 1

The correct option is C $9E$

Using Volume conservation,
$1000\times r^3=R^3$
or
$R=10r$
Also,
$E=4\pi R^{2}T$
$\therefore E=4\pi (10r{)}^{2}T$
or
$E/100=4\pi r^{2}T$
$\therefore$Total final surface energy= $1000\times E/100$= $10E$
Total Initial Energy= E
Workdone in doing that= 9E