# Homework Help: The uncertainty principle

1. Sep 26, 2010

### doubt

A particle is confined within a spherical radius of one femtometer(10^-15 m)?

Its momentum can be expected to be about-
1. 20 keV/c
2. 200 keV/c
3. 200 MeV/c
4. 2 GeV/c

How should I go about using HUP on a problem like this one? I tried substituting x=10^-15 meters in px=h/4 pi but the answer is wrong. Apparently because the problem is about volume.

2. Sep 26, 2010

### hikaru1221

We can only estimate the magnitude order of it; the answer is no way precise. Just pick the answer which is nearest to your answer.
By the way, the uncertainty in x-coordinate is 2R, not R.