Given :-
Mass of electron, m = 9.1 x 10^-31 kg.
Speed of electron, v = 5000 m /s.
Accuracy in speed measurement = 0.003 %.

According to Heisenberg's uncertainty principle, [(delta)x] [(delta)p] = h / 2 (pi)

So, Accuracy in location of position =
Uncertainty in position =
[(delta)x] = h / [2 (pi) {(delta)p}]
But p = m v,
So, [(delta)p] = m [(delta)v]
And so, [(delta)x] = h / [2 (pi) m {(delta)v}] ................(1)

Now, uncertainty in velocity, [(delta)v] = 5000 x [0.003 / 100] = 0.15 m / s.

So, from equation (1)
[(delta)x] = (6.6 x 10^-34 J.s) / [2 x 3.14 x (9.1 x 10^-31 kg) x 0.15 m /s]
= 0.7734 x 10^-3 J.s / [kg . m / s]
= 0.7734 x 10^-3 m
= 0.7734 mm.

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By :-   Dr. A. W. Pangantiwar