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Edexcel physics unit 6B (15 May 2014) watch

1. (Original post by Leil)
I will when i correct it.
Since you've done Jan 14, isn't it weird that we had to divide uncertainties with constants in the equations (Q1)?

and for Q3b, how did you find the unit for C? Cuz what i got was ms^2-ms^2.
So confused now...
yah it was weird, but had to do what they told us to do.
in Q3 at first i wrote C is the y-intercept. But then i noticed if C was a y-intercept its value will be zero. But in the next question they told us to find the unit, and for C to have a unit it needs to be a y-intercept. So i assumed C is the y-intercept, i live in another universe and the unit of C is unit of (T^2)h. and guess what!i do live in another universe!
jan 2014 was crazy!
2. (Original post by Leil)
I will when i correct it.
Since you've done Jan 14, isn't it weird that we had to divide uncertainties with constants in the equations (Q1)?

and for Q3b, how did you find the unit for C? Cuz what i got was ms^2-ms^2.
So confused now...
hey!about Q1, i just discussed it with my brother and found out it's not weird to divide by the constants. For example-
you have 10 mangoes with uncertainty 2
you ordered for half of what you had.
so if you had 12 mangoes u will get 6 , and if you had 8 u will get 4.
so uncertainty is divided by 2...
3. (Original post by ih8school)
In January 2014 paper why do we include the pi value when calculating uncertainty? I mean we're not supposed to include constants, but why is it still included in this paper?
when multiplying uncertainity by a constant, the absolute uncertainity is multiplied by the constant and the % uncertainity is left alone.
4. When a line goes through the origin, and has a positive gradient, we say the two variables are directly proportional to each other.
When a line curves with a positive gradient, we say that the two variables are inversely proportional to each other.
What do we call a line though, which is straight and has a negative gradient? Linear relationship?
5. (Original post by jtbteddy)
When a line goes through the origin, and has a positive gradient, we say the two variables are directly proportional to each other.
When a line curves with a positive gradient, we say that the two variables are inversely proportional to each other.
What do we call a line though, which is straight and has a negative gradient? Linear relationship?
Negative linear correlation.

I don't think the your second sentence is always true. It should properly be defined, and is difficult to judge if they are inversely proportional to each other or even if one inversely proportional to the square of the other.

To test a relationship in this paper I reckon we should just try and make a linear relationship of some variables and test it out in a graph. So more often that not for example if we want to see if a is inverse proportional to b we can draw a graph of a vs 1/b and this should be a straight line through the origin.
6. Does any one have the specification for this? I really need it, please! Give me the link or maybe if you can, upload it.I'd really appreciate it
7. (Original post by awesomesoccerfan)
Does any one have the specification for this? I really need it, please! Give me the link or maybe if you can, upload it.I'd really appreciate it
I posted it before! It is just sitting there on the edexcel website.

(Original post by RoyalBlue7)
Go through the IAL spec and under unit 6 it has all what we need to know so we can make sure we know what is expected from us

http://www.edexcel.com/migrationdocu...ion_Issue1.pdf
8. (Original post by RoyalBlue7)
I posted it before! It is just sitting there on the edexcel website.

I tried downloading it a few days back and got a 404 error...i tried looking for it today but couldn't find it..Thanks bro

Is this the practical one?
9. (Original post by RoyalBlue7)
Negative linear correlation.

I don't think the your second sentence is always true. It should properly be defined, and is difficult to judge if they are inversely proportional to each other or even if one inversely proportional to the square of the other.

To test a relationship in this paper I reckon we should just try and make a linear relationship of some variables and test it out in a graph. So more often that not for example if we want to see if a is inverse proportional to b we can draw a graph of a vs 1/b and this should be a straight line through the origin.

Okay, got it, thanks! If it's 1/b squared, would it still be a straight line?
10. (Original post by jtbteddy)
Okay, got it, thanks! If it's 1/b squared, would it still be a straight line?
If a was inversely proportional to the square of b then it would be a straight line. For example if a is the electrostatic force exerted by a charge and b the distance from the charge.

If it can be in the form y = mx + c where y is the variable on the vertical axis and x the variable in the x axis then it will be straight line.
11. On this specification for Unit 6 it says:
"identify the most appropriate apparatus, giving essential details-‐essential details may include the range and precision of instruments
and/or relevant dimensions of apparatus (eg the length of string used
for a pendulum)"

What do they mean by the range of an instrument? I know the precision of a vernier, micrometer, metre rule, protractor, stopwatch, but what is the range of these?

And what do they mean by the dimensions of apparatus? I know the formula for the time period of a pendulum which has the term length in it, but what do they exactly mean by this requirement?
Attached Images
12. International-spec-Physics.pdf (946.0 KB, 184 views)
13. (Original post by RoyalBlue7)
If a was inversely proportional to the square of b then it would be a straight line. For example if a is the electrostatic force exerted by a charge and b the distance from the charge.

If it can be in the form y = mx + c where y is the variable on the vertical axis and x the variable in the x axis then it will be straight line.
Kkay, so if I'd plot a against 1/b sqaured I'd get a straight line, right?
14. (Original post by jtbteddy)
Kkay, so if I'd plot a against 1/b sqaured I'd get a straight line, right?
Are you referring to a question or an example or anything? I can't be sure what a or b is.
15. (Original post by Cosmologist)
Ok, there are two types of precaution: technical precautions and safety precautions. Safety precautions are more frequently asked (some straightforward points, like 'keeping people away from radiation source', 'using tongs to handle the source', 'wearing goggles', etc). Technical precautions are those that you need to take into account to amend your experimental results. (in questions they mean by that ways to improve accuracy of the quantity you measure) For example, tech precautions could be:
- Stirring the liquid to produce even heating
- Placing thermometer away from walls and bottom of the container
- Insulation
- Repeat and average
- Measuring smth at multiple orientations (thickness of a coin, for instance)
- Providing good thermal contact between the apparatus
- Removing the heating element, whilst taking the readings
- Checking for zero error
- ... and so on.
Errors arise if (both) precautions are ignored
I think you got it.
You genius! Thank you soooo much
16. (Original post by kcapsoccer)
error has to do with the uncertainties , while precaution is related to the safety issues of the experiment
Thank you kcapsoccer
17. OKAY.
18. how can we investigate damped oscillation? plz anyone help me
19. OKAY. Here's whats important.

1 a When there is a single reading involved, then the uncertainty is the least count.
b If the reading is measured using a stop watch then the uncertainty is the reaction time. typically 0.1 s

2 a If multiple readings are involved, then the uncertainty is half range.
b If the half range value is less than least count or reaction time, then choose the least count or reaction time as the uncertainty

3 Percentage uncertainty is (Uncertainty/Measured value) * 100%

4 Percentage difference between an experimental value and a standard value is (Measured value - Standard value/ Standard value) * 100%

5 Percentage difference between two experimental values is (Difference between the two/ Average of the two) *100%

6 When quantities are added or subtracted then the final value should be stated to the least D.P of the the data values.

7 When quantities are multiplied or devided then the final value should be stated to the least SF of the data values

8 To check whether two experimental values are agreeing to each other
* Find the percentage difference
* Double the percentage uncertainties
* Compare the two. If percentage difference is greater than the percentage uncertainty then the values do not agree to each other. Otherwise they do

9 To check whether an experimental value agrees to a standard value
* Find the percentage difference
*Find the percentage uncertainty
* Compare the two. If percentage difference is greater than the percentage uncertainty then the values do not agree to each other. Otherwise they do

10 Instead of the above two methods you can use a range method. Find the extreme point(s) of the range(s) and see whether the other value lies within the range. If so then they agree

11 Uncertainty should be given to the same precision as the quantity value is given to.

12 When you multiply by a constant, percentage uncertainty remains the same but absolute uncertainties are multiplied

13 Why do we fold a paper many times to measure its thickness, This is because doing so reduces the percentage uncertainty. How? The precision of the instrument remains the same but the actual measured value has increased

14 Ways of reducing percentage uncertainty include choosing a more precise instrument and increasing the size of the measured value

15 Why are certain instruments suitable? For these questions comment on the precision and range of the instrument eg : "Measured value is many times greater than least count..Therefore less percentage uncertainty"

16 When finding the average of a set of values remember to neglect anomalous data.

17 When finding the gradient of the graph..use and draw a large triangle

18 Graph data should be given to 3SF. Data read from graphs should be precise to 3SF

19 Zero errors are an example of systematic errors. Parallax errors are a form of random errors. When explaining parallax always draw a diagram to illustrate your point. Do not use the term "ëye level". Instead say "align your eye with the scale"

20 Language of your answer is not important. Use bullet points if your more comfortable with it AND DRAW DIAGRAMS TO ILLUSTRATE POINTS.

HOW DID I FORGET THE MOST IMPORTANT BIT????

** When values are added or subtracted, their uncertainties are added. REMEMBER! Even if you subtract values you should add the uncertainties!

** And of course, when values are multiplied or divided, their percentage uncertainties are added.

20. Thanks a lot! This really helps!

(Original post by 55 %)
6 When quantities are added or subtracted then the final value should be stated to the least D.P of the the data values.

7 When quantities are multiplied or subtracted then the final value should be stated to the least SF of the data values
Shouldn't that be "divided"?
so for X+y, when X is 7000 and Y is 7.1, the answer should be 7007 (least d.p), and significant figures do not matter at all? Only decimal places?

(Original post by 55 %)
19 Zero errors are an example of systematic errors. Parallax errors are a form of random errors. When explaining parallax always draw a diagram to illustrate your point. Do not use the term "ëye level". Instead say "align your eye with the scale"
Could you please give more examples of systematic and random errors?

Thank you very much!
21. (Original post by RoyalBlue7)
Are you referring to a question or an example or anything? I can't be sure what a or b is.
Nvm, I got it, thanks anyways

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