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Thread: HSC Physics Marathon 2013-2015 Archive

  1. #76
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by Sy123 View Post




    q/m = 1 x10^5
    mv^2 /r = qvB (theta = 90degrees)
    q/m = v/rB

    v/r = q/m x B
    v/r =1 x 10^5 x 10
    r/v = 1 x 10^-6
    distance/speed = time
    therefore time = 1x10^-6 seconds



    maybe?
    2013 ATAR 98.00
    2014-2018 BOptometry(Hons)/BScience(Vision Science) @ UNSW

  2. #77
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    Re: 2013 HSC physics marathon

    Quote Originally Posted by Immortalp00n View Post
    The slingshot effect, defined as the increase in velocity given to a spacecraft because it enters the gravitational field of a planet as it passes by, is a technque used by Space agencies in accordance with physicists in order to take full advantage of a planets rotational motion in order to increase a particle's ( spacecraft) final speed.
    The slingshot effect is used by many spacecraft which travel within and beyond the solar system.
    A spacecraft passes close to a a planet such that its gravity pulls the spacecraft into an arc or circular motion.It leaves with the same speed relative to the planet, but its speed is increased when viewed from an alternate frame of reference such as the Sun.
    The acquired speed is large enough so that the spacecraft can travel away from the planet.
    Comparatively, a ball thrown from a person who is stationary would have speeds less than a ball thrown from a person who is running at an increasing or stationary speed. Thus the slingshot effect, also known as gravity assist trajectory is used in order to attain a significant change in speed and direction despite the very little expenditure of fuel, improving flight efficiency.
    Should possibly consider writing this as "increase in velocity, relative to the Sun", because relative to the planet it passes, no change in velocity is experienced.
    2013 ATAR 98.00
    2014-2018 BOptometry(Hons)/BScience(Vision Science) @ UNSW

  3. #78
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by yasminee96 View Post
    q/m = 1 x10^5
    mv^2 /r = qvB (theta = 90degrees)
    q/m = v/rB

    v/r = q/m x B
    v/r =1 x 10^5 x 10
    r/v = 1 x 10^-6
    distance/speed = time
    therefore time = 1x10^-6 seconds



    maybe?
    That looks correct to me, nice work.

  4. #79
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    re: HSC Physics Marathon Archive

    Almost a correct solution

    However, for one complete revolution the distance is r2pi.
    It's a minor error, probs only lose 2 marks
    Although in the future try not to just use formulae without thinking

  5. #80
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by yasminee96 View Post
    q/m = 1 x10^5
    mv^2 /r = qvB (theta = 90degrees)
    q/m = v/rB

    v/r = q/m x B
    v/r =1 x 10^5 x 10
    r/v = 1 x 10^-6
    distance/speed = time
    therefore time = 1x10^-6 seconds



    maybe?
    isn't it :

    t=2(r)(pi)/v

    t= 2(10^-4)(pi) = 6.2831*10^-4 seconds

    ??

  6. #81
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    Describe three applications of the CRT and all features and characteristics of each application. (8 marks)

  7. #82
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    bump

  8. #83
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive












  9. #84
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by Sy123 View Post


















    (F=mg, W= Fr (Tungsten = Francium )) (BUT REMEMBER THAT GPE IS ALWAYS NEGATIVE!!!)





    (1)


    (Draw a triangle of the object at rest at the starting position)


    (2)


    Therefore, substituting equation (2) into (1) gives us:





    Now someone have a go at my last question before I forget the band 6 response!!! (8 marks)

    Describe three applications of the CRT and all features and characteristics of each application. (8 marks)
    Last edited by anomalousdecay; 23 Apr 2013 at 8:18 PM.

  10. #85
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by anomalousdecay View Post






    (F=mg, W= Fr (Tungsten = Francium )) (BUT REMEMBER THAT GPE IS ALWAYS NEGATIVE!!!)





    (1)


    (Draw a triangle of the object at rest at the starting position)


    (2)


    Therefore, substituting equation (2) into (1) gives us:





    Now someone have a go at my last question before I forget the band 6 response!!! (8 marks)

    Describe three applications of the CRT and all features and characteristics of each application. (8 marks)
    I can't read it well but if you showed it, you showed it, nice work.

  11. #86
    Junior Member Hypem's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by Sy123 View Post


    5A anticlockwise through the loop?

  12. #87
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by Sy123 View Post
    I can't read it well but if you showed it, you showed it, nice work.
    Thanks.

    What code do you use for the font you have? I tried to use the same one but it didn't work.
    Also, sub- and super-scripts don't work here the same as word, so yeah I had troubles with that.

  13. #88
    Executive Member iBibah's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by anomalousdecay View Post
    Thanks.

    What code do you use for the font you have? I tried to use the same one but it didn't work.
    Also, sub- and super-scripts don't work here the same as word, so yeah I had troubles with that.
    It's Latex: http://www.codecogs.com/latex/eqneditor.php


    Question: Explain why the motor of an electric drill is more likely to overheat when the drill is experiencing a load.

  14. #89
    Executive Member bleakarcher's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by iBibah View Post
    It's Latex: http://www.codecogs.com/latex/eqneditor.php


    Question: Explain why the motor of an electric drill is more likely to overheat when the drill is experiencing a load.
    When the motor of an electric drill is experiencing a load, its rotational speed lowers which in turn lowers the back EMF of the motor. Net EMF = Supply EMF - Back EMF. If the back EMF is decreased, the net EMF increases and so does the current flowing through the coils of the motor. The greater the current flowing through the coils the greater the electrical power lost to heat by power loss=I^2*R making the motor more likely to overheat.
    Physics is to mathematics like sex is to masturbation.” —Richard Feynman

  15. #90
    Executive Member iBibah's Avatar
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    Quote Originally Posted by bleakarcher View Post
    When the motor of an electric drill is experiencing a load, its rotational speed lowers which in turn lowers the back EMF of the motor. Net EMF = Supply EMF - Back EMF. If the back EMF is decreased, the net EMF increases and so does the current flowing through the coils of the motor. The greater the current flowing through the coils the greater the electrical power lost to heat by power loss=I^2*R making the motor more likely to overheat.
    Good answer. Post a question if you like.

  16. #91
    Junior Member Hypem's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by anomalousdecay View Post
    Thanks.

    What code do you use for the font you have? I tried to use the same one but it didn't work.
    Also, sub- and super-scripts don't work here the same as word, so yeah I had troubles with that.
    If you couldn't be bothered learning LaTeX, then you can just use the equation system on Google Docs (https://drive.google.com/), then use http://puush.me/ to take screenshots of it.

    Insert -> equation gets you started and there's a toolbar for a bunch of mathematical symbols and what not.

    It's really, really easy to use. ^ is superscript, and _ is subscript, etc.

  17. #92
    Junior Member Hypem's Avatar
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    re: HSC Physics Marathon Archive

    Questions:

    1. Explain why Michelson and Morley expected a change in the interference pattern received by the detector of the interferometer.
    2. A circular disc of conducting material is rotating clockwise. The bottom part of the disc is in a magnetic field going into of the page. Explain what happens to the disc and why.
    Last edited by Hypem; 27 Apr 2013 at 2:00 AM.

  18. #93
    what is that?It is Cowpea RealiseNothing's Avatar
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    re: HSC Physics Marathon Archive

    Explain the purpose of using a radial magnet in a galvanometer.

  19. #94
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by RealiseNothing View Post
    Explain the purpose of using a radial magnet in a galvanometer.
    According to the equation F=BIL sinx , where x is the angle at which a conductor is orientated to an uniform magnetic field, once the galvanometer needle is moved, the force induced will vary as the needle moves. Radial magnetic fields are uniform within a consistent radius from the centre of the field, at the tip of the needle. This means that as the needle tilts, its angle to the radius of the circle of particular strength will be 90 degrees. This occurs because the needle and magnetic field form a radius and tangent.
    Hence, a radial magnetic field provides equal force on the needle, no matter how much it is tilted. Since a galvanometer detects tiny currents, it is necessary to have a uniform magnetic field as the needle is tilted, hence the use of the radial magnetic field.

    Someone do my question if they are bothered . 3 posts, but still failed to be answered.

    Describe three applications of the CRT and all features and characteristics of each application. (8 marks)
    Last edited by anomalousdecay; 30 Apr 2013 at 6:59 PM.

  20. #95
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive
















  21. #96
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive




  22. #97
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive








  23. #98
    Premium Member anomalousdecay's Avatar
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    re: HSC Physics Marathon Archive

    Sy are you doing q2q? I might do Age of Silicon or q2q.

  24. #99
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by anomalousdecay View Post
    Sy are you doing q2q? I might do Age of Silicon or q2q.
    I'm doing Astrophyiscs.

  25. #100
    This too shall pass Sy123's Avatar
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    re: HSC Physics Marathon Archive

    Quote Originally Posted by Sy123 View Post














    Hence we need to shrink the Earth to a radius r, whereby,





    Calculations then follow to find the new radius of the Earth

    ========

    A new follow up question:



    It isn't directly related to the Physics syllabus but I think its rather interesting, but of course can be answered with HSC physics knowledge, just a bit of imagination.
    Last edited by Sy123; 3 Jun 2013 at 12:02 AM.

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