Six molecules have speeds 2 units, 5 units, 3 units, 6 units, 3 units and 5 units respectively. The rms speed is

Options

(a) 4 units
(b) 1.7 units
(c) 4.2 units
(d) 5 units

Correct Answer:

4 units

Explanation:

v(rms) = √[(v₁² + v₂²+ ……. + v(n)²) / n] = √[(4+25+9+36+9+25) / 6]
= √(108 /6) = √(18) = 3 √2 = 3 × 1.414 = 4.242 units
i.e. 4 units is the approximately correct answer