# Homework Help: Quantum mechanics minimum uncertainty

1. Jun 15, 2008

### jalen

URGENT!! quantum mechanics question

1. The problem statement, all variables and given/known data

In the lungs there are tiny sacs of air, which are called alveoli. The average diameter of one of these sacs is 0.25nm. Consider an oxygen molecule(mass=5.3x10^-26kg) trapped with a sac. What is the minimum uncertainty in the velocity of this oxygen molecule?

2. Relevant equations

I'm not sure what equation I should use...then I'll post what the possible answer is

3. The attempt at a solution

2. Jun 15, 2008

### LHC

I'm reading a similar section in my physics textbook, and I came across an equation ... in the section for Heisenberg's uncertainty principle.

$$\Delta x \Delta p \geq \frac{h}{2\pi}$$, where h is Planck's constant.

Hope that helps?

3. Jun 15, 2008

### jalen

Hey LHC, thanks for the quick reply :)

I know that nm=r and kg=m but how would I sub it into the equation you mentioned?

4. Jun 15, 2008

### jalen

x--> uncertainty in particle's position...
p--> uncertainty in particle's momentum...

5. Jun 16, 2008

### Redbelly98

Staff Emeritus
So the equation will tell you the uncertainty in the momentum. Find that.

p.s. and watch the units ... use meters, kg, & sec for everything.