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Thread: Physics Exam Thoughts

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    Re: Physics Exam Thoughts

    Quote Originally Posted by 782341 View Post
    Am i the only one that didn't find the exam as easy as everyone is making it out to be? Did medical physics option btw
    I also did medical and thought some of the questions were a bit hard. MC was super tough and there wasnt a single question on any of the scientists in ideas to implementation. Wasted 2 days of studying all that.

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    Re: Physics Exam Thoughts

    Nice and straightforward - I thought medical physics was pretty good too.
    What was the velocity of the projectile on the moon - I did it wrong and got 400ms^-1?
    For anyone who did medical physics, the thing about compare ultrasound A and B, was it right to say that they will both be reflected in the same proportion because the boundary was the same regardless of which side they approached from??
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    Re: Physics Exam Thoughts

    Quote Originally Posted by bjw22 View Post
    Nice and straightforward - I thought medical physics was pretty good too.
    What was the velocity of the projectile on the moon - I did it wrong and got 400ms^-1?
    For anyone who did medical physics, the thing about compare ultrasound A and B, was it right to say that they will both be reflected in the same proportion because the boundary was the same regardless of which side they approached from??
    Yep I also got around 400, I think 464 to be exact.
    Delta(KE) = -Delta(EP) was my method
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    Re: Physics Exam Thoughts

    Yeah i think thats right for the medical question, thats what I said. and i also got 400ms^-1 cause i tried to do suvat
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    Re: Physics Exam Thoughts

    Quote Originally Posted by Drdusk View Post
    Yep I also got around 400, I think 464 to be exact.
    Delta(KE) = -Delta(EP) was my method
    Lol idk what I was doing, I found the acceleration and then subbed it into a projectile motion equation - knew it was wrong at the time too given that acceleration isn't constant at all heights so ripppp
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    Re: Physics Exam Thoughts

    Quote Originally Posted by Drdusk View Post
    Yep I also got around 400, I think 464 to be exact.
    Delta(KE) = -Delta(EP) was my method
    I also got 464 but ive heard from people that this was the wrong answer
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    Re: Physics Exam Thoughts

    You had to do the a change in GPE = kinetic energy, so then the change in GPE that we worked out you equate to 1/2 *mv^2

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    Re: Physics Exam Thoughts

    Quote Originally Posted by 782341 View Post
    I also got 464 but ive heard from people that this was the wrong answer
    They be trippin haha

    It has to be, what method did they use?
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    Re: Physics Exam Thoughts

    Quote Originally Posted by Drdusk View Post
    They be trippin haha

    It has to be, what method did they use?
    I think they used delta ke=delta gpe instead of -delta gpe

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    Re: Physics Exam Thoughts

    Quote Originally Posted by 782341 View Post
    I think they used delta ke=delta gpe instead of -delta gpe
    Yep that's definitely wrong. I initially did that accidentally.
    Using that you get a velocity that's greater than the initial velocity. It is losing KE as it gains EP when it goes higher.
    Hence the final velocity must be less!
    Last edited by Drdusk; 1 Nov 2018 at 2:40 PM.
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    Re: Physics Exam Thoughts

    would the b6 cut off be around 85?

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    Re: Physics Exam Thoughts

    Quote Originally Posted by Exp View Post
    would the b6 cut off be around 85?
    I reckon maybe about there comparing rawmarks.info, it seems easier than some past papers in parts so that should be about right - a tad higher perhaps if NESA be cruel.
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    Re: Physics Exam Thoughts

    Would you not just derive orbital velocity from centripetal force = gravitational force? Then get 1480ms^-1? OOOOH was it not asking for orbital velocity?

    See overall, I thought the paper was conceptual and actually difficult, but if you are a "good student" you wouldn't have gotten fucked over like 2017 last q would've fucked most students regardless of your ability, study preparation etc. This paper really favoured students who studied, as you'd struggle otherwise ~ Gravitional vs electric definition, photocell and solar cell, electricity in the home and the projectile error and velocity questions were all quite conceptual, and I'd argue they are difficult. Although I think I got them all quite well, except the electricity one xP
    Last edited by supR; 1 Nov 2018 at 2:46 PM.
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    Re: Physics Exam Thoughts

    Whoa what an interesting and challenging test that challenges us in unique and reasonable ways.
    (Insert multiple choice and graph question)
    NESA - "Hahahaha lets make the cut-off 90'
    For velocity, did anyone get 1122ms?
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    Re: Physics Exam Thoughts

    Quote Originally Posted by supR View Post
    Would you not just derive orbital velocity from centripetal force = gravitational force? Then get 1480ms^-1?

    See overall, I thought the paper was conceptual and actually difficult, but if you are a "good student" you wouldn't have gotten fucked over like 2017 last q would've fucked most students regardless of your ability, study preparation etc. This paper really favoured students who studied, as you'd struggle otherwise ~ Gravitional vs electric definition, photocell and solar cell, electricity in the home and the projectile error and velocity questions were all quite conceptual, and I'd argue they are difficult. Although I think I got them all quite well, except the electricity one xP
    It's not orbital velocity though. It was vertical velocity only right?

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    Re: Physics Exam Thoughts

    Quote Originally Posted by Shadowfaxx View Post
    Whoa what an interesting and challenging test that challenges us in unique and reasonable ways.
    (Insert multiple choice and graph question)
    NESA - "Hahahaha lets make the cut-off 90'
    lol I hope not

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    Re: Physics Exam Thoughts

    Quote Originally Posted by supR View Post
    Would you not just derive orbital velocity from centripetal force = gravitational force? Then get 1480ms^-1?

    See overall, I thought the paper was conceptual and actually difficult, but if you are a "good student" you wouldn't have gotten fucked over like 2017 last q would've fucked most students regardless of your ability, study preparation etc. This paper really favoured students who studied, as you'd struggle otherwise ~ Gravitional vs electric definition, photocell and solar cell, electricity in the home and the projectile error and velocity questions were all quite conceptual, and I'd argue they are difficult. Although I think I got them all quite well, except the electricity one xP
    It said the projectile is projected upward, nothing about it orbiting. Remember throwing a projectile doesn't always mean it will achieve orbit.
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    Re: Physics Exam Thoughts

    Quote Originally Posted by supR View Post
    Would you not just derive orbital velocity from centripetal force = gravitational force? Then get 1480ms^-1?

    See overall, I thought the paper was conceptual and actually difficult, but if you are a "good student" you wouldn't have gotten fucked over like 2017 last q would've fucked most students regardless of your ability, study preparation etc. This paper really favoured students who studied, as you'd struggle otherwise ~ Gravitional vs electric definition, photocell and solar cell, electricity in the home and the projectile error and velocity questions were all quite conceptual, and I'd argue they are difficult. Although I think I got them all quite well, except the electricity one xP
    I dont think it mentioned it was orbiting

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    Re: Physics Exam Thoughts

    What final velocity did everyone get for the 20kg mass at 500km question?

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    Re: Physics Exam Thoughts

    something like 426m/s

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    Re: Physics Exam Thoughts

    4EEF4C81-EAB1-42BA-AC36-BB8A05A9E1D2.jpegIm seeing a common answer 426ms too this isnt my working out but saw it somewhere else
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    Re: Physics Exam Thoughts

    Quote Originally Posted by Drdusk View Post
    It relies on the particle ionizing the water vapor around it. Alpha particles are really highly ionizing hence they don't make it much past where they're generated(hence their path is short).

    Beta particles are much less ionizing and hence similarly their paths are long
    My understanding was that alpha was thicker and shorter (as you said) but beta was zig-zaggy/bendy. I put gamma as source Y since it was straight lines and also faint.

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    Re: Physics Exam Thoughts

    Quote Originally Posted by maxcf212 View Post
    My understanding was that alpha was thicker and shorter (as you said) but beta was zig-zaggy/bendy. I put gamma as source Y since it was straight lines and also faint.
    Yeah beta is technically zig-zaggy, but it complied more with beta than Gamma. Gamma doesn't produce continuous tracks. Rather they are very short dots which are at a distance away from the source.
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    Re: Physics Exam Thoughts

    Yeah I've realised my mistake now guys about orbital velocity grrrr ~ Hopefully I get a mark for it ://
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    Re: Physics Exam Thoughts

    The question said to ignore orbital velocity and rotational of the moon. And over the 500km altitude the acceleration change would be to large to be a projecitle motion question. So the kinetic energy which was equal to the work done could be derived from part i). 1.26x10^7= 1/2mv^2
    hence v=1122m/s thoughts?

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