If a nucleus disintegrates i two two nuclear parts which have their velocities in ratio 2 : 1 . The ratio of their nuclear sizes will be .

Question

$(a)\;2^{\large\frac{1}{3}} : 1\qquad(b)\;2 : 1\qquad(c)\;4 : 1\qquad(d)\;1 : 2^{\large\frac{1}{3}}$