Let uncertainty is position denoted by (del)x and uncertainty in momentum denoted by (del)p.

(del)x is equal to 2 * (del)p
Or, (del)x * (del)p = h/4 pie
Or, 2 * (del)p^2 = h/4 pie
Then solve it.
(del)p will be equal to (1/root 2*2) * (root over of h/pie).
Then substitute (del)p = m * (del)v since the mass is not uncertain.
Therefore, (del)v will be (1/2*root m) * (root over of h/pie).