Given :-
Mass of electron, m_e = 9.1 x 10^-31 kg.
Mass of bullet, m_b = 50 gms = 50 x 10^-3 kg.
Velocity of both electron and bullet, v = 300 m /s.
Accuracy in velocity measurement = 0.01 %.

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] = 300 x [0.01 / 100] = 0.03 m / s.

So, i) For electron, from equation (1)
[(delta)x] = (6.6 x 10^-34 J.s) / [2 x 3.14 x (9.1 x 10^-31 kg) x 0.03 m /s]
= 3.86 x 10^-3 J.s / [kg . m / s]
= 3.86 x 10^-3 m

And, ii) For bullet, from equation (1)
[(delta)x] = (6.6 x 10^-34 J.s) / [2 x 3.14 x (50 x 10^-3 kg) x 0.03 m /s]
= 0.703 x 10^-31 J.s / [kg . m / s]
= 0.703 x 10^-31 m

We can say from these result that for larger objects i.e bullet uncertainties are negligible whereas for objects of atomic dimensions i.e. electron uncertainties are significant.

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By :-   Dr. A. W. Pangantiwar