\( \Rightarrow 30 = 240{\left( {\frac{1}{2}} \right)^n}\)
\( \Rightarrow {\left( {\frac{1}{2}} \right)^3} = {\left( {\frac{1}{2}} \right)^n}\)
==> \(n=3\)
\(\therefore\) \(\frac{t}{{{T_{1/2}}}} = 3\)
\( \Rightarrow\frac{{{v^2}}}{r} = \frac{{{n^2}{r^2}}}{{4{\pi ^2}{m^2}{r^2}}}= 20\) મિનિટ
$_1{H^2}{ + _1}{H^2}{ \to _2}H{e^4} + Q$