If uncertainities in the measurement of position and momentum of an electron are equal, then uncertainity in the measurement of its velocity is approximately:
8.0 X1012m s-1
m2 Δv2 = h4π
Δr = 12m√hπ = 12 × 9.1 × 10−31(6.6 × 10−343.14)12
= 8 × 1012 m/sec