Heisenberg's Uncertainties, question

[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.

 

[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)