# Uncertainty question

1. Dec 6, 2005

### Pepsi24chevy

In an atom, an electron is confined to a space of roughly 10^-10 meters. If we take this to be the uncertainty in the electron's position, what is the minimum uncertainty in its momentum?

delta(x)delta(p)>h (this is how it was derived in the previous parts to the problem)
Ok so i know px = mvx and m = 9.11X10^-31 kg and that delta px = 10^-10(px). I guess where i am stuck is, what do i do with the velocity term?

2. Dec 6, 2005

### Galileo

You are not asked about the velocity. You are asked about the uncertainty in momentum. So you got $\Delta x \Delta p \geq \hbar$ (or without the bar, depening on what version your book has).

So you know $\Delta x$, that was given and you are asked the minimum value $\Delta p$ can take without violating the inequality. You should be able to tell that immediately from the equation. Or least least without reference to other relations.

Last edited: Dec 6, 2005
3. Dec 6, 2005

### Pepsi24chevy

am i missing some or would it be 1.05e-34J/10e-10?

4. Dec 6, 2005

### Galileo

That's right. Simply $\Delta p_{min}=\hbar/\Delta x$. What would you be missing?

5. Dec 6, 2005

### Pepsi24chevy

well the answer should be in kg*m/s thats why i feel i am missing something, but its probably just a conversion or something?

6. Dec 6, 2005

### Galileo

The answer is in kg m/s, since that is the unit of momentum. The units of h is Js. Since J=Nm=kgm^2/s^2 you can work it out.