# Homework Help: Heisenberg's Uncertainties, question

1. Sep 6, 2006

### kanki

I'm so confused of the Heisenberg's Uncertainties...

Here's a question i have to solve, although it looks very easy but my understanding of Heisenberg's Uncertainties is still shallow.

Fuzzy a quantum mechanical duck lives in a world which h = 2 PI Js. Fuzzy has a mass of 2.0 kg and initially is known to be within a pond of 1m wide.
- The minimum uncertainty in his speed?
- Assuming the uncertainty in speed prevails for 5.0s, determine uncertainy in position after that time.

This is my attempt to solve the first one:
Of course I have to apply Heisenberg's Uncertainties here.
m x (uncertainties in speed) x (uncertainties in location) => h/4PI
the mass is 2.0kg, but the uncertainty in location, is it half of the width or it's the width??
I'm still not good in determining the uncertainties.

2. Sep 6, 2006

### tim_lou

i think it should be half the width. because the uncertainty can be positive and negative. Let's say a particle is observed to be at 0, the uncertainty is 1 unit, so the particle should be within [-1,1] (width 2 units)