Uncertainty in percentage


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Chinyere Okeke 2J
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Uncertainty in percentage

Postby Chinyere Okeke 2J » Sun Oct 25, 2020 2:01 pm

What is the uncertainty when it is in percentage. Like for example, if a problem says an e- has a velocity of 4.5 m/s with an uncertainty of 1% is the delta-v 1 or is it 4.5(0.01)?

John Pham 3L
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Re: Uncertainty in percentage

Postby John Pham 3L » Sun Oct 25, 2020 2:04 pm

That should be correct. You just multiply the percentage to the value given to find the uncertainty.

Leo Naylor 2F
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Re: Uncertainty in percentage

Postby Leo Naylor 2F » Sun Oct 25, 2020 2:05 pm

The delta-v is 4.5(0.01), as you guessed. Multiply the percentage uncertainty by the velocity to find the absolute uncertainty.

Christine Ma 3L
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Re: Uncertainty in percentage

Postby Christine Ma 3L » Sun Oct 25, 2020 2:25 pm

Whenever you're unsure, you can also use the units to help you. Uncertainty in velocity (Δv) should have the units m/s so you would multiply the % by the velocity to get the uncertainty in velocity in meters per second. Hope this helps.

Khoa Vu 3l
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Re: Uncertainty in percentage

Postby Khoa Vu 3l » Sun Oct 25, 2020 3:09 pm

Adding on to what the other posts have said, multiplying your velocity by the decimal form of your percentage should yield the change in velocity. However, you should keep in mind that for uncertainties, the uncertainty can be both additive and subtractive. For example, the 1% uncertainty of 4.5 is .045. This could mean that the velocity is either 4.545 or 4.455. You would need to find the difference between these two velocities in order to get the absolute velocity change.

Arya Adibi 1K
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Re: Uncertainty in percentage

Postby Arya Adibi 1K » Sun Oct 25, 2020 6:42 pm

The percentage uncertainty represents the percent of the originally velocity that is uncertain. So in this case it would be 4.5 m/s +/- 0.01(4.5 m/s)

IshanModiDis2L
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Re: Uncertainty in percentage

Postby IshanModiDis2L » Sun Oct 25, 2020 8:24 pm

That should be correct but I would also suggest using the units to check your work when doing it.

Kyle Dizon 3A
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Re: Uncertainty in percentage

Postby Kyle Dizon 3A » Sun Oct 25, 2020 8:45 pm

Relying on the units will help with your confusion. Also, you can attempt to multiply the percentage to find the value of the uncertainty.

Susanna Givan 2B
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Re: Uncertainty in percentage

Postby Susanna Givan 2B » Sun Oct 25, 2020 11:54 pm

Multiplying is the correct procedure, then? Thank you so much for your clarification, it really helped me understand percentage uncertainty.


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