Clark Kent Posted August 3, 2011 Report Share Posted August 3, 2011 Hi everyone. 2 questions. In going through some past paper marking schemes, ive noticed that the answers arent always kept exactly as they have been calculated, they often get rounded to a number of significant figures. The number isn't always consistent either. So i'm confused as to how many decimal places or significant figures i have to round to in the actual IB exam? DO i just follow the prac guidelines and not exceed the number of sig figs or dp's the original data had? Also, with the prac, do all the data in the same column (e.g. 10 different points for surface area) have to have the same number of significant figures? or decimal places? i've heard some people say dp's and some say sig figs... which one is right? Thanks alot in advance!! Reply Link to post Share on other sites More sharing options...
Keel Posted August 3, 2011 Report Share Posted August 3, 2011 Hi everyone. 2 questions. In going through some past paper marking schemes, ive noticed that the answers arent always kept exactly as they have been calculated, they often get rounded to a number of significant figures. The number isn't always consistent either. So i'm confused as to how many decimal places or significant figures i have to round to in the actual IB exam? DO i just follow the prac guidelines and not exceed the number of sig figs or dp's the original data had? Also, with the prac, do all the data in the same column (e.g. 10 different points for surface area) have to have the same number of significant figures? or decimal places? i've heard some people say dp's and some say sig figs... which one is right? Thanks alot in advance!! Hi, This is what we do for chem, not sure whether it applies to physics. As a rule of thumb you round your final answer to the same number of significant figuers as the least accurate piece of data given to you. E.g. F=ma, where m=20.2 and a=0.32 m is rounded to 3 sf while a is rounded to two. Thus the answer of F being 6.7064 would be rounded to 2 sf of 6.7 As for your DCP question, it does not really matter. What matters is that you are consistent in your rounding. (Remember you should be presenting raw data with relation to the precision of the piece of equipment.) Hope this helps. Reply Link to post Share on other sites More sharing options...
ChikkyD Posted August 3, 2011 Report Share Posted August 3, 2011 I have a feeling it's to 3 significant figures in pracs and the like, but for questions, it's to 3 significant figures OR, if they're not available, the least amount of significant figures. That is what I have been told Hope it helps! Reply Link to post Share on other sites More sharing options...
Ezeh Posted August 6, 2011 Report Share Posted August 6, 2011 You can only be as accurate as the data you have been given. If you have been given data to only 2 s.f. then only answer with 2 or else you will most likely be awarded your accuracy penalty. If, however you have an answer that has been calculated with more than 3 s.f. then you can answer with only 3 and you will not lose a mark Reply Link to post Share on other sites More sharing options...
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