textbook 1B.5

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Catherine Bubser 2C
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Joined: Wed Sep 30, 2020 9:45 pm

textbook 1B.5

Postby Catherine Bubser 2C » Mon Oct 26, 2020 1:43 pm

Could someone explain why delta v is multiplied by 2 in part A of this example? The denominator as a whole is also multiplied by 2 because of the proportions so I'm confused as to why the uncertainty in the speed has to be multiplied additionally.

Yasmina Zaarour 1G
Posts: 60
Joined: Wed Sep 30, 2020 9:51 pm

Re: textbook 1B.5

Postby Yasmina Zaarour 1G » Mon Oct 26, 2020 1:51 pm

For the right side of the Heisenberg equation, they used h bar/2 instead of h/4pi. H bar is h/2pi, so either expression works. Sometimes, people use hbar because it is a simplified version of the equation.

Melis Kasaba 2B
Posts: 61
Joined: Wed Sep 30, 2020 9:49 pm

Re: textbook 1B.5

Postby Melis Kasaba 2B » Mon Oct 26, 2020 1:57 pm

The problem says the speed is known to within +/– 1.0 mm/s. This means that the range of possible values (delta v) would be twice that. For example, if the speed was 100 mm/s and it was known within +/– 1.0 mm/s, it could range from 99 mm/s to 101 mm/s, with a difference of 2.0. The 10^–3 comes from converting mm/s to m/s, and then that number has to be multiplied by 2.0 to account for the + 1.0 m/s value and the –1 m/s value.

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