# Uncertainty Principle

1. Sep 29, 2009

### Epif

1. The problem statement, all variables and given/known data
http://img340.imageshack.us/img340/3249/question.jpg [Broken]

2. Relevant equations
P=h/lambda
E=p^2/2m

3. The attempt at a solution

Well, I calculated P using a wavelength of .1 femtometer. Then I plugged it into the energy equation. However, I got 1.5e14 eV, while the answer sheet says it's supposed to be 12 GeV. Have I done something wrong wrong? On the answer sheet my professor calculated P, and I got the same answer he got, but after that he just says therefore E=12GeV, not showing how he came to that conclusion.

Thanks for any help!

Last edited by a moderator: May 4, 2017
2. Sep 29, 2009

### Fightfish

You cannot neglect relativistic effects at such high energies, thus the equation
$$E = \frac{p^{2}}{2m}$$ does not hold.
Instead you should use the relativistic equation
$$E^{2} = m_{0}^{2} c^{4} + p^{2} c^{2}$$

3. Sep 29, 2009

### Epif

Ahh that makes sense and gives e the right answer. Thanks!