MAY13 Physics tz2 " exponential" question P2

[IBN95]

Hi all, i just wanted to ask how was the exponential question needed to be done? I mean we all did it differantly, some proved that it was inversly proportional, while others used [ Y1(square) / x1 should equal Y2( square) / x2 ]

Personally, i have solved each and every measurement question ranging from 2007 - 2012, and never have i ever encountered exponential, i think the IB should not have used this question, and will expect a very large proportion of people missing those 4 marks.

[Elsherif M Ahmed]

If those 4 marks are the only missed ones then it's OK , physics is done, don't bother yourself and focus on the next subject , best wishes

[Garmr]

Hi all, i just wanted to ask how was the exponential question needed to be done? I mean we all did it differantly, some proved that it was inversly proportional, while others used [ Y1(square) / x1 should equal Y2( square) / x2 ]

Personally, i have solved each and every measurement question ranging from 2007 - 2012, and never have i ever encountered exponential, i think the IB should not have used this question, and will expect a very large proportion of people missing those 4 marks.

I agree with you. The exponential question totally caught me off guard and I think I spent far more effort on that data analysis than on any other paper.

Anyway, I said something like the relationship should be in the form of V = V_oe^-kt or something like that, then I disproved it by showing that the constant k is different for two different values.

[Giveme45]

Hi all, i just wanted to ask how was the exponential question needed to be done? I mean we all did it differantly, some proved that it was inversly proportional, while others used [ Y1(square) / x1 should equal Y2( square) / x2 ]

Personally, i have solved each and every measurement question ranging from 2007 - 2012, and never have i ever encountered exponential, i think the IB should not have used this question, and will expect a very large proportion of people missing those 4 marks.

I agree with you. The exponential question totally caught me off guard and I think I spent far more effort on that data analysis than on any other paper.

Anyway, I said something like the relationship should be in the form of V = V_oe^-kt or something like that, then I disproved it by showing that the constant k is different for two different values.

I did the same but k was actually similar for me o.O

[Pedro9604]

didnt expect exponential, I was prepared for directly proportional relation if the straight line goes trought the origin NOT an exponential

[difiCa]

Anyway, I said something like the relationship should be in the form of V = V_oe^-kt or something like that, then I disproved it by showing that the constant k is different for two different values.

Precisely what should have been done. Cannot confirm that the hypothesis is wrong or right though, I showed k was dissimilar but considering that it was during the last 2 minutes of the exam, I did not really think too hard about it.

[IB-Adam]

Used two methods, and both clearly showed that it was not exponential at all.

[Giveme45]

Used two methods, and both clearly showed that it was not exponential at all.

I integrated the function and checked the constant of integration at different points and i got something like 0.07(=0.1) and 0.1 -> thus exponential. Might be wrong, who knows, dont care ^^

[IB-Adam]

S

Used two methods, and both clearly showed that it was not exponential at all.

I integrated the function and checked the constant of integration at different points and i got something like 0.07(=0.1) and 0.1 -> thus exponential. Might be wrong, who knows, dont care ^^

Haha I think you made it too complicated.

y= k x^n

Two values had to be solved in this case, the k-constant, and the exponent value n.

1. Use two points, solve the simultaneous equation.

2. Check using a third point and solve for either constant.

You have to lose 30 marks in order to lose your 7 on P2 so relax I screwed up P3 so badly so I will definitely not get a 7..

[Giveme45]

S

Used two methods, and both clearly showed that it was not exponential at all.

I integrated the function and checked the constant of integration at different points and i got something like 0.07(=0.1) and 0.1 -> thus exponential. Might be wrong, who knows, dont care ^^

Haha I think you made it too complicated.

y= k x^n

Two values had to be solved in this case, the k-constant, and the exponent value n.

1. Use two points, solve the simultaneous equation.

2. Check using a third point and solve for either constant.

You have to lose 30 marks in order to lose your 7 on P2 so relax I screwed up P3 so badly so I will definitely not get a 7..

Haha where do the 30 marks come from?

[Kasper]

I just stated that if it was exponential then lg(whatever was on the Y-axis) versus lg(whatever was on the X-axis) would be linear. Then I calculated these values at two different points and found the relationship not to be linear and hence the original relationship was not exponential.

[-._._.-]

I treated it like a half-life graph. If it was exponential, then the 'half-life' would be constant. And it wasn't so I said it wasn't exponential.

[difiCa]

God the IB examiners are going to have fun looking at the various methods used to solve this question and deciding how to grade them. I wanna see the mark scheme next year.

[micogo]

I treated it like a half-life graph. If it was exponential, then the 'half-life' would be constant. And it wasn't so I said it wasn't exponential.

That's exactly what I did! I thought that for it to exponential, then values at each period of time would have to follow a geometric sequence - and they didn't. So I said it wasn't exponential.

I agree though, that was an unfair question. It would be hard to determine, especially for people who take maths studies, for example, because it isn't in the physics book at all.