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April 20, 2024, 07:59:29 am

Author Topic: Question about systemic air resistance errors  (Read 2402 times)  Share 

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Question about systemic air resistance errors
« on: August 03, 2021, 08:20:02 pm »
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Hi guys,
Today I had a sac which labelled air resistance as ‘systemic’ and asked us for a way to remove the extent of this error.
Whilst I now believe that the answer should have been to conduct an experiment in a room with less wind etc, I wrote that one must figure out the wind speed and then mathematically calculate what the speed would have been if there was no air resistance (considering air resistance is the same in each trial)

Is this possible to do? If so, why//why not? Any help would be appreciated

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mabajas76

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Re: Question about systemic air resistance errors
« Reply #1 on: August 04, 2021, 12:11:44 am »
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More info on the experiment would be needed.
Air resistance is fairly easy to find, it is equal to the velocity sqaured times a constant k, which is typically something like 0.002. So at 10 meters a second for a 10kg block, the air resistance is 0.2N and the weight force is 100 newtons. So really it can be neglected at low speeds. Note that the surface area and shape of the object will change the resistance but the point I was making was that air resistance can just be ignored in many senarios.
However in the context of your question, it seems to be testing your knowledge of errors/experimental practices. In experiments, a systematic error means it is an error which is constant with the experiemnt ie in a real world scenario there will always be resistance in wires in circuits and air resistance, but these can be foudn using a set method/equation, they don't really change in nature they r just a constant source of error. Since its systematic, it follows a system or set rule which means it can be calculated.

Now onto what you said: Conducting the experiment in a vaccum is the single best way to eliminate the error, however this is not always practical to accomplish (perfect vaccums r hard to make), so since the error is systematic, u can just subtract the error it causes.
However I don't particulary like your wording. "Wind speed" is incorrect, something can have speed yet have no net force acting on it, air has very little mass and therefore very small KE and momentum so it will hardly change the direction/acceleration. Air resistance is a force pushing against the block, but wind speed is not a force.
So for an offcial answer I would put these points (I put them in dot point form):
-Best way is to conduct experiment (assuming it is trialed multple times and averages r taken) in a vaccum close to the Earths surface (Gravity changes at higher up).
-However this is not practical and so another way is to find the error provided and systematicly subtract it. This is done by:
-Find the acceleration of the block with no air resistance using theroy,
-Find the average acceleration of the block in the trials
-Subtract theroy from trial, that is the acceleration in the opposite direction (if it was an incredibly annoying and stupid question, may give u density of air and some measurments and then u can go mass times acceleration =fnet of air resistance but it doens't seem to be asking that).
-Explain that this approach can be applied constantly no matter the number as the error is said to be systematic.
Tell me if I got anything wrong, cheers.
"Don't give up, and don't put too much effort into things that don't matter"-Albert Einstein, probably.