## Heisenbergs equation example from lecture

$\Delta p \Delta x\geq \frac{h}{4\pi }$

Kaylee Nezwek 1D
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### Heisenbergs equation example from lecture

Dr. Lavelle did an example in class on Heisenbergs equation, in which he used an incorrect atom model. For an H atom, the e- was confined to the nuclear diameter, 1.7 * 10^-15 m.

Using ∆p ∆x ≥ h/4π, ∆p was greater than or equal to 3.1*10^-20 kg/m/s^-1.

However, then using ∆p = Me- (∆v), and rearranging it to be ∆v = ∆p/Me-, he plugged in ∆v = 3.1*10^-20 kg/m/s^-1 / 9.1*10^-31 kg. Where did 9.1*10^-31 kg in the dominator come from/how did he get it?

Also, will problems on this equation only be like this, where we will get an unrealistic number and therefore have to prove that atoms are a lot bigger than the nucleus? Like in other words, are we always using the equation to prove some indeterminacy, thus our answers will always be unrealistic when using the equation?

LaurenChoi_1J
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Joined: Wed Sep 30, 2020 9:48 pm

### Re: Heisenbergs equation example from lecture

9.2*1-^-31 is the mass of an electron I believe, which is where he got the number.

Kaylee Nezwek 1D
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### Re: Heisenbergs equation example from lecture

Ah I didn't realize it was the same for all electrons, thank you!!

LaurenChoi_1J
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Joined: Wed Sep 30, 2020 9:48 pm

### Re: Heisenbergs equation example from lecture

Kaylee Nezwek_2G wrote:Ah I didn't realize it was the same for all electrons, thank you!!

No problem! Oh and in my reply I meant 9.1*10^-31, not 9.2*10^-31, my bad!

Joel Meza 3I
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Joined: Wed Sep 30, 2020 9:56 pm

### Re: Heisenbergs equation example from lecture

That number is the mass of an electron, it's just a given and it is listed on the "Constants and Equations" handout Lavelle provided for us to use during our midterms and final in case you don't memorize it along the incoming weeks.