dessskris Posted November 24, 2011 Report Share Posted November 24, 2011 what do you mean?I wouldn't suggest talking about physics UNLESS it affects your model greatly and you are VERY sure it's correct. Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 24, 2011 Report Share Posted November 24, 2011 How do you justify that it is a power function? Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 24, 2011 Report Share Posted November 24, 2011 well as accurate as possible!at least get the shape right...hey sorry one more question; if i model a power function : y=axb and then i substitute values of x and y to make a system of equation, i get somewhat reasonable answers if i stubstitue time values for x but if i stubstitute +Gx values for x then it seems completely wrong. Therefore time should go on the x axis?because actually it made more sense to me the other way around but it seems to work better if time is on the x axisplease help!!!! Reply Link to post Share on other sites More sharing options...
sljj Posted November 24, 2011 Report Share Posted November 24, 2011 Sorry. How do I determine which function to model (for the first part). My teacher said I can't just guess from a bank of functions or base it on the shape which it looks like. Reply Link to post Share on other sites More sharing options...
dessskris Posted November 25, 2011 Report Share Posted November 25, 2011 Well its not really physics, like the curve has to be changed somehow and its simply a limitation to the values of Gz.but still, if you change it due to some physics stuff you HAVE to explain it, correctly.How do you justify that it is a power function?talk about the characteristics of a power functionhey sorry one more question; if i model a power function : y=axb and then i substitute values of x and y to make a system of equation, i get somewhat reasonable answers if i stubstitue time values for x but if i stubstitute +Gx values for x then it seems completely wrong.Therefore time should go on the x axis?because actually it made more sense to me the other way around but it seems to work better if time is on the x axisplease help!!!!it should work both ways, but oh well.it's okay to put it on the x-axis as long as you can justify why.Sorry. How do I determine which function to model (for the first part). My teacher said I can't just guess from a bank of functions or base it on the shape which it looks like.actually it's totally up to you... you can try plotting the data in your GDC and look which regression fits best, and choose that one (but don't write in your paper you chose it because you tried all regressions and it looks the best...) Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 25, 2011 Report Share Posted November 25, 2011 How do you justify that it is a power function? talk about the characteristics of a power function i know but which characterisitcs? i googled all over the internet and couldn't find anything im so sorry but i have one more question; should i refer to time and gx as t and gx or as x and y when i talk about substituting them into the equation for example? thank you soooo much! Thanks Reply Link to post Share on other sites More sharing options...
dessskris Posted November 25, 2011 Report Share Posted November 25, 2011 isn't this your work? if I told you which characteristics, I would be giving you an answer. or, just BS it? this part is a little bit of maths combined with some BS. it's totally up to you what to define the variables as, but I suggest putting and because if you just use x and y, the examiner might forget what each of x and y represents since the letters are not related to the variable name.. not saying that they'd actually forget but it might confuse them. you as the writer might forget too. Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 25, 2011 Report Share Posted November 25, 2011 ok thanks!!!i'm sorry, i didn't mean to ask for too much Reply Link to post Share on other sites More sharing options...
dessskris Posted November 25, 2011 Report Share Posted November 25, 2011 it's okay, I don't mind. it's just that we can't reveal answers in the forum! so yeah I try not to discuss it.. Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 25, 2011 Report Share Posted November 25, 2011 it's okay, I don't mind. it's just that we can't reveal answers in the forum! so yeah I try not to discuss it.. yeah sure i get your point Reply Link to post Share on other sites More sharing options...
IB 2012 Posted November 25, 2011 Report Share Posted November 25, 2011 ok i know you will be annoyed but i hope this question is not too direct If i have done two systems of equations, i selected points which were rather far apart is that ok? for axb if i found b then if i substitute it into either of the two equations i should get the same value for a, but its not. any ideas why that might be the case? thanks!!! Reply Link to post Share on other sites More sharing options...
dessskris Posted November 26, 2011 Report Share Posted November 26, 2011 nahh that's fine, ask me whatever you like but if I'm not supposed to answer that I just hope you'll understand. yes that's fine. choose points that you think will give you the correct shape. hmmm you should be getting the same values of a and b... maybe you did a calculation mistake? note that: I don't know what you did wrong though if you could message me your working, I could help spot the mistake Reply Link to post Share on other sites More sharing options...
dessskris Posted November 26, 2011 Report Share Posted November 26, 2011 idk I don't use geogebra, but try to use your TI. I somewhat prefer TI for its features and beautiful interface. Reply Link to post Share on other sites More sharing options...
ring Posted November 26, 2011 Report Share Posted November 26, 2011 my revised function is actually worse than my other one. should i still keep it and just acknowledge that it is worse? Reply Link to post Share on other sites More sharing options...
hlloyd2206 Posted November 27, 2011 Report Share Posted November 27, 2011 The assignment asks for appropriate variables on the data... does this mean manipulated, controlled and responding like in physics?? And what would be an example of constraints on the data, does the fact that it is not an average of many test subjects so only represents the tolerance of one person count? Because it doesn't specify how the data was collected. Help!! Reply Link to post Share on other sites More sharing options...
dessskris Posted November 27, 2011 Report Share Posted November 27, 2011 haha not exactly but you can say one variable is dependent and the other is independent. perhaps you could mention what the letters +Gx and t represent, and define their domains. the constraints: can t be negative? can +Gx be negative? can they be zero? can they be decimal or have to be integers? stuff like that. Reply Link to post Share on other sites More sharing options...
dessskris Posted November 27, 2011 Report Share Posted November 27, 2011 my revised function is actually worse than my other one. should i still keep it and just acknowledge that it is worse?it means you weren't doing the right thing. what did you do to revise your function? repeat the revision correctly or just scrap it off. Reply Link to post Share on other sites More sharing options...
ring Posted November 27, 2011 Report Share Posted November 27, 2011 my revised function is actually worse than my other one. should i still keep it and just acknowledge that it is worse?it means you weren't doing the right thing. what did you do to revise your function? repeat the revision correctly or just scrap it off.for the last bit, with the vertical G-force. when it says what changes have to be made to fit the new data, do i simply discuss for instance shift or find values for a and b ... or do i do the whole procedure that i did for the horiziontal g force again to find a model function? i am just scared that i will get penalized for understanding the question wrong Reply Link to post Share on other sites More sharing options...
demon Posted November 27, 2011 Report Share Posted November 27, 2011 I have the exact same problem that IB 2012 had, no matter whether I used +Gx as the x axis or if I used time as the x axis, there is no equation (model) that seems to fit the graph. I really need help. Also my equation is in the ax^b format, is this correct? Reply Link to post Share on other sites More sharing options...
dessskris Posted November 27, 2011 Report Share Posted November 27, 2011 I actually suggest that you use translation and stretch. however if that fails really badly and you're stuck, I guess you could re-model the whole thing. Reply Link to post Share on other sites More sharing options...
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