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Physics Uncertainties

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I'm doing a Physics lab report on uncertainties.

What we did was, we measured our reaction time, i.e. we used a meter stick, one student was releasing it (quietly) and other one tried to catch it as soon as possible after he/she sees that the meter stick has been released. We measured our "catching" 10 times for each hand. Now we have to find the uncertainties in our results, but the problem is that I have some formulas etc. but i have no idea how to use them, and how to find the uncertainties.. Our teacher didn't really explain how to do it, so I'm totally lost... HELP!

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As I see that the page that Tim Tam left doesn't work you might have to reconsider your possibilities. The uncertainty will depend on two things, in the smallest division of the meter stick and the smallest division of the apparatus in which you measured the reaction time. Be conscious that there's always some errors in this procedure/measurement with the meter stick. First of all, even when we try to measure things very accurately, it is never possible to be absoñutely certain that the measurement is perfect.

I'll assume that you know that errors can be divided in random or systematic. If readings of a measurement are above and below the true value with equal probability, then the errors are random. Usually this kind of errors are made or caused by the person making the measurement, for example, the orror due to a person's reaction time is a random error. There you'll have, besided the uncertainties, the most common error in your report. Maybe the person who was in charge of measuring the reaction time, I'm gonna supose now that you used a chronometer, didn't started the counting when the meter stick started falling or didn't stop the measurement when the other person catched the meter stick either with the right hand or the left hand, so that would be a random error. I don't really think you had systematic errors as it depends on the system or apparatus used and I can be sure the ones you used are simple so yeah..

Another distinction in measuring things is between presicion and accuracy. If most of the results were made in a certain(small) lapse of time then the results were precise and even accurate but if the person didn't catch the meter stick as soon as it was released and the length in which he catched the apparatus varies a lot, the results were neither precise nor accurate. However, if the person catch the ruler, meter stick in a certain position most of the times, the results were precise but not accurate.

I hope you understand.

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Guest PoisonousPumpkin

I love how you explain physics in such a specific and simple way! Congrats :D

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