Example 1.7a in the Textbook  [ENDORSED]


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Danielle Sumilang - 1F
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Joined: Fri Apr 06, 2018 11:05 am

Example 1.7a in the Textbook

Postby Danielle Sumilang - 1F » Sat Apr 28, 2018 11:34 pm

Hello!

Can someone please explain how the uncertainty in the position of a marble of mass 1.0 g given that its speed is known to within 1.0 mm s^-1 was calculated? I understand that the equation for the uncertainty principle is delta p x delta >= 1/2 h bar, but where did the equation delta p = m times delta v come from? Thank you!

AshleyLamba1H
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Re: Example 1.7a in the Textbook

Postby AshleyLamba1H » Sun Apr 29, 2018 12:49 am

The equation to find momentum is p = mv (momentum = mass * velocity). To find the change in momentum, you would put a delta in front of every variable except mass, because in the case of the marble, its mass is not changing.

Phil Timoteo 1K
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Re: Example 1.7a in the Textbook

Postby Phil Timoteo 1K » Sun Apr 29, 2018 1:57 pm

P=mv

Andre-1H
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Re: Example 1.7a in the Textbook  [ENDORSED]

Postby Andre-1H » Sun Apr 29, 2018 6:07 pm

Yep just to add on it makes sense that the second equation is like that because for an object like a marble its speed can change, meaning that its momentum can change, leading to the delta symbol. However, its mass is constant, and cannot change.

QuincyH1G
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Re: Example 1.7a in the Textbook

Postby QuincyH1G » Sun Apr 29, 2018 7:03 pm

Like this example, when calculating the uncertainty in position, is the uncertainty in velocity always positive.


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