Change in Velocity Uncertainty


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Racquel Fox 3L
Posts: 35
Joined: Wed Sep 30, 2020 10:11 pm

Change in Velocity Uncertainty

Postby Racquel Fox 3L » Mon Oct 26, 2020 7:55 pm

Your bowling ball of mass 4.02kg rolls down a lane with a speed of 2.35 +/- 0.1m/s.
What is the minimum indeterminacy of its position? Can you blame the Heisenberg
Uncertainty Principle when your ball misses the pins?

I'm getting confused on when you multiply the velocity by 2 or when you just use the given uncertainty. How do you know which one to do?

Cecilia Cisneros 1J
Posts: 75
Joined: Wed Sep 30, 2020 9:45 pm

Re: Change in Velocity Uncertainty

Postby Cecilia Cisneros 1J » Mon Oct 26, 2020 7:59 pm

You multiply the given uncertainty of your velocity when its a "±". Because the uncertainty is the difference between the ± 0.1m/s
Uncertainty of velocity = difference = (0.2m/s -0.0m/s) = 0.2m/s
Subtracting the difference is the same as multiplying by 2.

You do not multiply 2 when they explicitly state what the uncertainty of velocity. Hope that helps!

Samuel Flores 2C
Posts: 35
Joined: Wed Sep 30, 2020 9:51 pm

Re: Change in Velocity Uncertainty

Postby Samuel Flores 2C » Mon Oct 26, 2020 8:18 pm

Hello! Usually, if the problem gives a range of values (e.g. 500 m/s ± 1m/s), then we will use that range of values and multiply by 2 to get the uncertainty.

However, if the problem explicitly says "The uncertainty in __ is ...", then this is a signal for you to just use that exact value as the uncertainty. In other words, if the problem explicitly tells you the uncertainty of a value, then simply use that number in the Heisenberg Uncertainty Equation.

Hope this helps!

aashmi_agrawal_3j
Posts: 43
Joined: Wed Sep 30, 2020 9:39 pm

Re: Change in Velocity Uncertainty

Postby aashmi_agrawal_3j » Wed Oct 28, 2020 5:30 pm

You multiply by 2 when there is a +/- because the uncertainty can be double the amount due to this. You use the given uncertainty if it gives you a percentage without the +/- or doesn’t explicitly tell you to double the value.

Alessia Renna 1D
Posts: 36
Joined: Wed Sep 30, 2020 9:36 pm

Re: Change in Velocity Uncertainty

Postby Alessia Renna 1D » Sat Oct 31, 2020 9:59 am

Because it says +/- you would multiply by two, making the uncertainty in velocity 0.2m/s. You would then multiply this by the mass given in the problem to get delta P. You can then plug that delta P value into the uncertainty equation (given to you on the constants and equations sheet) in order to find delta X.


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