Heisenbergs uncertainity principle for an electron

1. Sep 26, 2012

DODGEVIPER13

1. The problem statement, all variables and given/known data
The speed of an electron is measured to within an uncertainty of 2e4 m/s. What is the size of the smallest region of space in which the electron can be confined?

2. Relevant equations
Diracs Constant=ΔxΔp
p=mv

3. The attempt at a solution
what I did was (Diracs Constant)/mv = Δx, (1.054560653e-34)/((9.109e-31)(2e4))=6nm this is this incorrect but I dont understand why?

2. Sep 27, 2012

Rajini

Hi,
I am not sure, I may be wrong.
Use Heisenberg uncertainty principle:
$$\Delta x \Delta p ≥ \hbar/2.$$
The given value is not the speed of electron. It is the uncertainty of speed.
Got it?

3. Sep 27, 2012

sweet springs

Hi. Not value but only order of value has meaning in this situation. Order of nano meter seems fine. What is the 'correct' answer you have got?

4. Sep 27, 2012

DODGEVIPER13

Sweet springs the correct answer is 5.8nm what I get is 6nm I know it's so close but it's not what I'm getting. Rajini given the uncertainty of speed how then would I find speed go the electron so I can find p.

5. Sep 27, 2012

DODGEVIPER13

Ok I'm starting to think I got the right answer after using wolfram I get 5.78 I am starting to think my calculator has some kind of rounding algorithm