Help with lab question(percent error)

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Homework Help Overview

The discussion revolves around a lab question related to circular motion, specifically focusing on calculating the percent error associated with measurements taken during the experiment. The original poster presents data including total mass, radius, and period, but expresses uncertainty about how to approach the calculation of percent error.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants question the definitions of terms like "uncertainty" and "error," and seek clarification on how to calculate the theoretical values needed for the percent error. There are discussions about the certainty of measurements and the formulas used to derive the period of motion.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the problem and questioning the assumptions made about the measurements. Some guidance has been offered regarding the need to clarify what is meant by "the trail" and how to approach the calculation of percent error.

Contextual Notes

Participants note potential uncertainties in the measurements of mass, radius, and period, suggesting that these factors may affect the accuracy of the percent error calculation. There is also mention of the precision of the period measurement and the implications of using theoretical versus actual values.

packerfan128
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Homework Statement


Lab on circular motion. The class swung a mass in a circular motion by a string.
--Find percent error of the trail.
Total mass=0.25kg
radius=.448 meters
period=.427 seconds

Homework Equations



I am not sure

The Attempt at a Solution



This is one of those problems that drew me a blank... I have no idea where to start. It would be great if someone could just start me off with what i am trying to take the % error of. I know that % error is actual/theoretical X 100%. I just don't know what I am trying to solve. Thanks.
 
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I call "uncertainty" what you call "error".
What is the uncertainty of the Total mass? Of the radius and the period?
Once you know the total mass, radius and period, how did you calculated the trail? (I mean, what formula did you use?).
 
the total mass is certain... we mass the iron on the end of the string. The radius is also certain... I measured it with a ruler. I guess the only thing that could really be uncertain is the period (we measured it with a top watch). The formula is T=2(pi)*(SquROOT(length/9.8)) So would i calculate what the theoretical period would be, then divide it by the period i got?
 
packerfan128 said:
the total mass is certain... we mass the iron on the end of the string. The radius is also certain... I measured it with a ruler. I guess the only thing that could really be uncertain is the period (we measured it with a top watch). The formula is T=2(pi)*(SquROOT(length/9.8)) So would i calculate what the theoretical period would be, then divide it by the period i got?

I don't think there's something certain. You said the mass is certain but I guess you measured it with a balance and my guess is that it's accuracy is about 0.01g.
So you'd have [tex](0.25 \pm 0.01 ) g[/tex]. You realize the uncertainty is 4% which is not 0% as you suggested.

By the way, I don't understand what you had to find. Why did you measured a period?
Another thing :
period=.427 seconds
I don't want to scare you but how did you do such a precise measurement which was done handily?
Last thing :
I know that % error is actual/theoretical X 100%.
is of no help here. For example what would you take as a theoretical length, mass, etc.?
I wish someone else could help you more than I do.
 
packerfan128 said:
--Find percent error of the trail.

What is meant by "the trail", and how do you calculate it?
 

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