Recent content by uart

  1. U

    2Arg(z+1) = arg(z)

    Yes you're correct, you need to show a rhombus specifically for the angle bisect property. Sorry, I deleted that quoted post just before reading your reply and was about to acknowlege the correction.
  2. U

    2Arg(z+1) = arg(z)

    Note that the lines from O to 1, from O to z and from z to z+1 form a parallelogram rhombus. The result follows immediately from the parellelogram rhombus property that the diagonals bisect the corner angles.
  3. U

    HSC Chemistry 2021 Exam Solutions

    I think that the problem with the equation given in Q37 is that the SO3^(2-) just wont exist in aqueous equilibrium with H+, not without also forming HSO3-. I'm starting to think that maybe the correct answer to the last question is that an equilibrium cannot be established with only the...
  4. U

    HSC Chemistry 2021 Exam Solutions

    Guys, I've got a query about the equilibrium constant (approx 1 x 10^-9) in the last question. I agree that it was very easy to algebraically come up with that solution, but I'm trying to understand the utility (usefulness) of that overall equilibrium equation. I'm probably doing something dumb...
  5. U

    Maths Ext 2 Predictions/Thoughts

    It looks dirty Agreed that it looks dirty, but it's probably still valid. The point is that it's not about proving that it is the correct answer, it's about proving that the other surd is not the correct answer. It would of course be invalid to try to use a calculator to prove that it was...
  6. U

    Chemistry Exam Predictions/Thoughts

    You can also verify it's C by reading off the exact values of the concs, and then calculating the equilb constant ratios with both the initial and final values. You'll find A just doesn't work numerically. The soln given by Beanie above is a lot quicker though.
  7. U

    Math Ext 1 Predictions/Thoughts

    Yeah, it definitely should be like the blue one, and it kind of needs some sloppy working to get that red soln. Look for example at the column of slope lines immediately to the right of P (at x about -0.8). There you can see that TL's red solution had to take a gradient that was significantly...
  8. U

    Physics HSC Predictions/Thoughts

    Ok I see, I hate it when that happens. MC can be annoying like that, with so little time it's very easy to know your stuff but still make some really minor mistakes that will lose you the marks. Meanwhile someone who knows close to nothing can often jag about 50%.
  9. U

    Physics HSC Predictions/Thoughts

    With const acceleration from rest you get: x = \frac{1}{2} a_x t^2 y = \frac{1}{2} a_y t^2 Eliminate "t" to get a linear relation between x and y. - KE increases from (2 phi - phi) to (4 phi - phi), so KE is tripled. - v is proportional to sqrt(KE), so v is increase by factor sqrt(3) - r...
  10. U

    Physics HSC Predictions/Thoughts

    Thanks notime, you're absolutely right. I only skimmed through this late last night and didn't notice that mass loss was per minute (yes I calculated per second). The other question 14 again you are correct. Equal an opposite forces, not acceleration. Thanks for pointing that out as I had a...
  11. U

    Physics HSC Predictions/Thoughts

    I only got to look at the paper late tonight so have just skimmed through, but my prelim MC solns are 1 ........... 5 B C D B A 6 ...........10 D C D C B 11 ........ 15 A D B A C 16 ....... 20 B C A A D Edited 14 and 16 thanks to notime123
  12. U

    Physics HSC Predictions/Thoughts

    Yep, ans to Q18 is (a). With accelerating motion (from rest) in both x and y directions then the trajectory is linear. (Even if the accelerations are unequal.) After the x accel is removed (E field removed) it follows the usual parabolic trajectory.
  13. U

    Maths Ext 2 Predictions/Thoughts

    Also, neither the Itute nor TL solns provided a satisfactory explanation for why the negative \sqrt{5} solution was invalid in Q14c(ii). \cos^2{(\pi/10)} = \sqrt{\frac{5 \pm \sqrt{5}}{8} } Itute gave no reasoning for selection of the +ive inner surd, while TL reasoned that cos^2() must be...
  14. U

    Physics HSC Predictions/Thoughts

    Ok cool. So it could be anyone then, like even a teacher or other staff member. I think it's a good thing to get the papers circulating asap, so as to facilitate discussion of the questions while they're still fresh in people's minds. And as you say, they're going to be officially released soon...
  15. U

    Physics HSC Predictions/Thoughts

    Hopefully you'll get an answer straight from the horses mouth. But I'm assuming that either someone manages to sneak a copy of the paper out of the exam, or they manage to photo/scan it during the examination.
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