Batman2k1
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#1
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When answering a physics question, how many significant figures do i do for the question?

Lets say there are 2 values, 20, 200, do i do the sf to 2 sf or 3sf???

can someone help me on this?
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MyChemicalGarden
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If the question tells you explicity how many sig figs, use that for the rest of the question, do not add any more sig figs in later parts of the same question.

If it is not explicitly given, it depends on the context and you need to use common sense.
For example, if I said I have a mass of rougly 7kg and throw it with a force of around 7.6N, it wouldnt be smart to say the acceleration is 1.081, as I have added accuracy to my answer which never existed in the first place. It would be best to say 1.1ms^-1, which is the greatest precision I had to calculate the acceleration in the first place.

hope that makes sense
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username3947384
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(Original post by MyChemicalGarden)
If it is not explicitly given, it depends on the context and you need to use common sense.
For example, if I said I have a mass of rougly 7kg and throw it with a force of around 7.6N, it wouldnt be smart to say the acceleration is 1.081, as I have added accuracy to my answer which never existed in the first place. It would be best to say 1.1ms^-1, which is the greatest precision I had to calculate the acceleration in the first place.
Would it not be 1ms^-1 because 1 (7kg is 1 significant figure) is the smallest significant figure within your calculations?
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Batman2k1
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(Original post by xstatic)
Would it not be 1ms^-1 because 1 (7kg is 1 significant figure) is the smallest significant figure within your calculations?
Yes i was thinking this too.. could you elaborate on this please
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BTAnonymous
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(Original post by xstatic)
Would it not be 1ms^-1 because 1 (7kg is 1 significant figure) is the smallest significant figure within your calculations?
yes, you need to use the lowest accuracy in the question, otherwise it's not accurate (seems counter intuitive by rounding your answer but it's true!).

If you have values of 1.00, 2.0119 and 2.001, you round to 3 sig fig.

So the example used with 7kg and 7.6N, that should be rounded to 1 sig fig.

It is imperative however to show how you get 1ms^-1. In other words, show what number you rounded from to get 1ms^-1, otherwise you'll get no credit on some questions (stupid but they're marks you shouldn't be losing).
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MyChemicalGarden
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(Original post by Batman2k1)
Yes i was thinking this too.. could you elaborate on this please
Yes, sorry, i meant to put 7.0kg. The main point is not to add accuracy which never existed in the first place
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Batman2k1
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Oh okay, thanks guys.
I think i know why, i get marks deducted when carrying out a practical, as i do an accuracy that was not required for the raw data.
What if the results i got was 0, 5.5, 10,
if i put 0 as a result, would it be 0.0 or just 0, i seen my friend who just did 0, and i just put the accuracy of 0 to 0.00 in this case.
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