# Four particles have speed 2,3,4 and 5 cm/sec respectively. Their RMS speed is

$(a)\;3.5cm/S\qquad(b)\;(\large\frac{27}{2})cm/S\qquad(c)\;\sqrt{54} cm/S\qquad(d)\;\large\frac{\sqrt{54}}{2}cm/S$

$U_{rms} = \sqrt{[\large\frac{2^2+3^2+4^2+5^2}{4}]}$
$\;\;\;\;\;\;\;\; = \sqrt{[\large\frac{4+9+16+25}{4}]}$
$\;\;\;\;\;\;\;\;=\sqrt{[\large\frac{54}{4}]}cm S^{-1}$