# Uncertainty Principle and speed

1. Mar 11, 2009

### forty

Suppose Fuzzy, a quantum-mechanical duck, lives in a world in which h = 2pi J.s Fuzzy has a mass of 2.0kg and is initially known to be within a range of 1.0m wide.

(a) What is the minimum uncertainty in his speed.

delta(x)delta(p) = hbar/2

hbar/2 = 1/2
delta(x) = 1
p = mv = 2v

so uncertainty in v is 1/4 ?

Is this in anyway right :S ?

(b) Assuming this uncertainty in speed to prevail for 5.0s, determine the uncertainty in his position after this time.

I'm guessing 2.2m (but really no idea what so ever)

Any help would be greatly appreciated.

2. Mar 12, 2009

### kreil

$$\Delta x \Delta p >= \frac{\hbar}{2} = \pi$$...(1)

since $${\hbar} = 2 \pi$$...

(a) use (1)

(b) I would guess you just use $$x = vt$$