# Physics Practical (AS)

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#1
http://papers.xtremepapers.com/CIE/C..._w12_qp_34.pdf

In question 2 part h, how can I show whether or not the relationship is supported by calculating two values of k?
(you may have to go over question 2 from the beginning to know what we're doing here)
0
7 years ago
#2
http://papers.xtremepapers.com/CIE/C..._w12_qp_34.pdf

In question 2 part h, how can I show whether or not the relationship is supported or not by calculating two values of k?
(you may have to go over question 2 from the beginning to know what we're doing here)
The relationship is supported if k is a constant.
You have found two values of k. Is it constant?
The two values will not be exactly the same because of experimental uncertainties.
You have calculated in the previous parts, the uncertainty in t and in sin theta.
So are the two values of k you have there "equal" within the limits of the uncertainty. Or do they differ by an amount that lies outside the range of experimental uncertainty?
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#3
(Original post by Stonebridge)
The relationship is supported if k is a constant.
You have found two values of k. Is it constant?
The two values will not be exactly the same because of experimental uncertainties.
You have calculated in the previous parts, the uncertainty in t and in sin theta.
So are the two values of k you have there "equal" within the limits of the uncertainty. Or do they differ by an amount that lies outside the range of experimental uncertainty?
Which experimental uncertainty do we compare it to? The one for t or sin theta?
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#4
(Original post by Stonebridge)
The relationship is supported if k is a constant.
You have found two values of k. Is it constant?
The two values will not be exactly the same because of experimental uncertainties.
You have calculated in the previous parts, the uncertainty in t and in sin theta.
So are the two values of k you have there "equal" within the limits of the uncertainty. Or do they differ by an amount that lies outside the range of experimental uncertainty?
I know that I've to calculate the percentage difference between the two ks and then compare this to some percentage uncertainty. I just don't know which uncertainty to compare it to.
0
7 years ago
#5
The % uncertainty in the value of k is the sum of the % uncertainties in t and sin theta
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#6
(Original post by Stonebridge)
The % uncertainty in the value of k is the sum of the % uncertainties in t and sin theta
But since sin theta is under a radical, I'd say the % uncertainty in the value of k is % uncertainty in t + 0.5(% uncertainty in sin theta), right?

But I mean, why would they require us to do all this for only 1 mark? I just don't get it.
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#7
(Original post by Stonebridge)
The % uncertainty in the value of k is the sum of the % uncertainties in t and sin theta
Do you think I could maybe calculate the percentage difference between the two values of k and compare it to an assumed percentage uncertainty of say, 20%?

If the percentage difference is less than or equal to 20%, then the relationship is supported, otherwise it isn't.

I'm not sure if this is correct. What do you think?
0
7 years ago
#8
But since sin theta is under a radical, I'd say the % uncertainty in the value of k is % uncertainty in t + 0.5(% uncertainty in sin theta), right?

But I mean, why would they require us to do all this for only 1 mark? I just don't get it.
Oops yes I just looked at the question again.
Its root sin theta so yes it is half the % uncertainty in that.
You already have the uncertainties worked out in this question.

It does seem a lot for one mark.
For example, if your total % uncertainty was, say, 10% and your two values of k were within 10% of each other I would be happy with the result.
Beyond that, without the mark scheme, I'm not sure what they are expecting. It's only one mark. I would have thought any attempt at relating the (%) difference between the two k values to the uncertainty in the experimental values of t and sin theta would gain the mark.
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