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  1. D

    Urgent help require in p5!

    Accuracy is the technical term for the level of uncertainty in the measurements. They are +/- 1% for example. Validity and reliability are overall assessments of the correctness of the experimental procedures, the collection of the data and the methods used to evaluate the data. The Biology...
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    Cie grading scheme

    Just to clarify (or perhaps confuse) this issue for the unwary. The statement in the syllabuses about the grading scheme does not mean that if the total number of points available is 270 then you need 90% or 243 points to obtain an A* nor does it mean that if you obtain 243 points you will...
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    Chemistry: Post your doubts here!

    The preferred reagent to use is supposedly SOCl2 because the by-products are both gases that can easily be removed from the product. CH3CH2CH2CH3OH (l) + SOCl2 (l) -----> CH3CH2CH2CH2Cl (l) + HCl(g) + SO2 (g) With the other reagents the by products are liquids that are more difficult to...
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    I am doing physics AS again but...............

    It was a pleasure, I enjoyed thinking about your questions. I hope the document I posted helps you with your doubts. Try doing the second part of problem 4, paper 2 June 2009 to see if you understand the different arrangements of springs and post any further doubts that occur to you.
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    Mathematics: Post your doubts here!

    I agree that yours is a better solution since I applied the double angle formula when I didn´t need to and I did not solve for x like the question said. In math questions it is always good to go back and reread the question after you have done the calculations to make sure that when you think...
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    I am doing physics AS again but...............

    If I have attached the file correctly then here are the formulas and relationships. Do not just memorize them, try to understand them.
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    I am doing physics AS again but...............

    In that situation there are not only moments but torque. The side with spring A would tend to move down and the side B tend to would move up. I have some difficulties in picturing what the equilibrium of the system would be like, I think you would need to take into account the weight of the beam...
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    help grades calculation

    I have not seen the November 2011 thresholds but let me give my explanation based on what I understand and the thresholds for June 2011. On the published thresholds there is the phrase, “The A* threshold is calculated using the difference between A and B as a starting point. “ In the June...
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    Mathematics: Post your doubts here!

    I will give it a try. Separate variables: dx/(x+1) = cos(2O)/sin(2O)dO I do not seem to have the symbols on my computer so O = theta integrating left side is just ln(x+1) apply double angle formula to two terms on right side. cos2(O) -sin2(O) d(O) 2sin(O)cos(O) simplify cos(O)...
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    I am doing physics AS again but...............

    If the two springs were not made of the same material or of the same length then they would have different spring constants. Analysis of parallel springs requires that the springs be identical otherwise the situation becomes too complicated and is not likely to appear on an AS exam. However in...
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    I am doing physics AS again but...............

    Parallel and series springs is not really a distinct topic. Having two identical springs in parallel means that the weight is divided between them, so their extension 1/2 that of a single spring. When they are in series each spring is subjected to the same force so each will have the extension...
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    A level Biology: Post your doubts here!

    Unsaturated phospholipids have a lower melting point than saturated phospholipids. This is because the unsaturated phospholipids have a bend in the long molecule so the molecules do not fit so easily in a crystal structure. Lowering the melting point of the phospholipids in the membrane will...
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    Urgent help require in p5!

    The independent variable is the condition that you control and you vary and the dependent variable is the variable that you measure. That is it, there is nothing else to it and it doesn´t matter whether it is biology, chemistry or physics. You plot the independent variable on the x-axis and...
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    Mathematics: Post your doubts here!

    If the line makes an angle of 120 degrees with the positive x-axis then the gradient of the line is equal to the tan (120) which is equal to -sqrt(3). The line perpendicular will have a gradient of 1/sqrt(3). The rest of the question I don´t understand.
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    My AS components grade...can i get A* now?? HELPP!!

    You probably were just at the threshold for an A. I do not understand how the threshold for an A* is calculated but it is my understanding that for the overall grade it is the total points that is used for determining the final letter grade, meaning that a point is a point no matter where it...
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    pls, can someone tell me why the melting point of graphite is higher than that of diamond?

    Yes, each carbon in graphite is covalently bonded only to three other carbons in graphite. This leaves each carbon with an unpaired electron that can migrate in the 2-dimensional network. To cite the Wikipedia article on carbon, “Because of the delocalization of one of the outer electrons of...
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    IGCSE CHEMISTRY HELPP neededd

    Electrons always move to the positive terminal of the battery and away from the negative terminal of the battery. In electrolysis you are pulling electrons from the positive electrode and pushing them onto the negative electrode. Once you remember this basic principle the equations follow. At...
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    pls, can someone tell me why the melting point of graphite is higher than that of diamond?

    In graphite each carbon is linked to three others by covalent bonds. In diamond each carbon is linked to four others by covalent bonds. So it seems paradoxical that diamond would have a lower melting point. There are Van der Waals forces between the layers of graphite but these are relatively...
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    pls, can someone tell me why the melting point of graphite is higher than that of diamond?

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