Pre Lab, how to find uncertainty

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Homework Help Overview

The discussion revolves around calculating the uncertainty or standard deviation of the average force (Fave) in a pre-lab context. Participants are exploring how to determine the uncertainty associated with measurements and calculations involving Fave.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants are discussing the relationship between fractional errors in multiplication and division, questioning how these apply to the calculation of uncertainty in Fave. There are attempts to clarify the mathematical expressions involved in these calculations.

Discussion Status

The discussion is ongoing, with some participants seeking clarification on the concepts of fractional error and how to apply them to the uncertainty in Fave. A specific formula for calculating the fractional error has been provided, but there is no consensus on the interpretation or application of this information yet.

Contextual Notes

Participants are working under the constraints of a pre-lab assignment, which may limit the information available for calculations. There is a focus on understanding the definitions and relationships between different types of uncertainties.

Habibrobert
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Hello,

I have been stuck on this prelab all day.I have finished all the questions except for the last one, where it asks you to find the uncertainty (or standard deviation) of Fave. I have tried every resource and nothing has helped so far. Any help would be great!

Thanks
 

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When you multiply or divide two numbers with fractional error f1 and f2 respectively, what is the resultant fractional error of the product or quotient? (Assuming normal error distributions).
 
Hello,

I'm really sorry but I don't understand what you mean?
 
Habibrobert said:
Hello,

I'm really sorry but I don't understand what you mean?

Like, (x +/-Δx) * (y +/-Δy) gives (xy +/- what)?

Annd division is just 1/multiplication so it follows the same rule.
 
The uncertainty in Fave, ΔFave, divided by the value of Fave (what rude man calls the fractional error) is given by

ΔFave/ Fave = Δ(Δp)/Δp + Δ(Δt)/Δt

where Δ(Δp) is the uncertainty in the change of the momentum and Δ(Δt) is the uncertainty in the time interval - see the summary at the end of
http://www.physics.mcmaster.ca/undergrad/Uncertainties/U.htm

What you need to calculate is then ΔFave.
 

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