A-level Physics Blog: D at AS to an A in Year 13

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    (Original post by Eimmanuel)
    In regard to the sign issue, as mike had suggested a useful technique and I would add to his suggestion.
    In kinematics for one or two dimensional problems, it is arbitrary to choose which direction is positive as long as you are consistent. If you find it difficult to choose, then stick to the usual Cartesian coordinate (xy plane).
    You may want to post the question you have problems in deciding the direction.
    Hey, it's funny you say that because I'm currently having problems with a question in my M1 textbook:

    " A particle is moving along the x-axis with constant deceleration 5ms-2. At time t=0, the particle passes through the origin O with velocity 12ms-1 in the positive direction. At time t seconds the particle passes through the point A with x-coordinate 8. Find
    (a) the values of t,
    (b) the velocity of the particle as it passes through the point with x-coordinate -8. "

    I'm so confused about which direction the particle is travelling in... left to right or right to left?
    And is the particle moving from x=0 to x=8 and then moving from x=0 to x= -8 ?
    And I suppose the acceleration is 5ms-2 one way and -5ms-2 the other way, but not sure which way round it is?
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    You can tell it's started moving left to right from the wording in the question. And the question implies that the deceleration acts to slow the particle's initial speed, so the acceleration acts from right to left, ie taking a negative sign.
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    (Original post by mik1a)
    You can tell it's started moving left to right from the wording in the question. And the question implies that the deceleration acts to slow the particle's initial speed, so the acceleration acts from right to left, ie taking a negative sign.
    Oh okay, I just got confused because the particle is at the origin at t=0, so if it started off at x= -8 , this would make the time at this point negative?
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    (Original post by jessyjellytot14)
    Oh okay, I just got confused because the particle is at the origin at t=0, so if it started off at x= -8 , this would make the time at this point negative?
    I'm not sure I understand. The particle is at x=0 when t=0. We aren't told what the particle is up to for t < 0, it could be anywhere.
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    (Original post by mik1a)
    I'm not sure I understand. The particle is at x=0 when t=0. We aren't told what the particle is up to for t < 0, it could be anywhere.
    Part (b) asks you to find the velocity of the particle as it passes through the point x = -8
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    (Original post by jessyjellytot14)
    Part (b) asks you to find the velocity of the particle as it passes through the point x = -8
    Ah. I guess if the thing is being accelerated leftwards (negative) for long enough, it actually stops moving the starts moving backwards. At some (positive) time it'll pass the origin and then go on to reach the point x = -8.
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    (Original post by Naruke)
    Taking AS+A2 Physics this year, so I'll stay tuned into this thread :P
    Same, I asked a few days ago and said why not.

    Only downside is this £40 textbook and no practical qualification.

    I HATE ISAs/EMPAs - pros of the new spec.

    I do OCR
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    (Original post by jessyjellytot14)
    Hey, it's funny you say that because I'm currently having problems with a question in my M1 textbook:

    " A particle is moving along the x-axis with constant deceleration 5ms-2. At time t=0, the particle passes through the origin O with velocity 12ms-1 in the positive direction. At time t seconds the particle passes through the point A with x-coordinate 8. Find
    (a) the values of t,
    (b) the velocity of the particle as it passes through the point with x-coordinate -8. "

    I'm so confused about which direction the particle is travelling in... left to right or right to left?
    And is the particle moving from x=0 to x=8 and then moving from x=0 to x= -8 ?
    And I suppose the acceleration is 5ms-2 one way and -5ms-2 the other way, but not sure which way round it is?
    As Mike had answered most of your queries, I would add a few points. I can see your confusion. Recall that I said I would avoid using the word deceleration. This problem brings out the reason and Mike had also commented that the sign of acceleration is only telling us half of the story.

    In this problem, the sign of velocity is already predetermined by the given x-coordinates.

    In the first 2.4s, the object is slowing down because the direction of acceleration and velocity are opposite.
    The velocity is towards right (At time t=0, the particle passes through the origin O with velocity 12ms-1 in the positive direction.) but the acceleration is towards left (which is why the problem stated deceleration, so is negative)

    At t = 2.4s the object comes to rest momentarily at x = 14.4 m and changes direction because of the negative acceleration.

    After t =2.4 s, the object is moving in the direction toward O (i.e. toward the left) but this time ( say t = 3.0 s), both the velocity (-3.0 m/s) and acceleration (-5 m/s2) are negative, so the object is speeding up instead of slowing down. (The use of deceleration is therefore inappropriate here, which I think can cause confusion.)

    At t = 4.8 s, the object returns to the origin O and moves with the velocity -12 m/s, in the negative direction.

    I think would be better if the first statement of the problem is written as

    "A particle is moving along the x-axis with constant acceleration 5 m s-2 in the negative direction."

    There are many such problems out there, so be careful. Hope that the examination board can really check through the problems of the text before endorsing them...
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    22/09/16



    M1: We answered some vertical suvat problems today which took up the whole double lesson. I find it so annoying how you have to use 9.8 as the value for g in M1 because I'm so used to using 9.81 in physics!
    In case, you haven't noticed, I'm including M1 in this thread because it is technically physics

    Physics: We briefly went over simple harmonic motion, simple harmonic oscillators and free & forced vibrations. I should probably re-write my notes soon because they look like trash lmao.

    After sixth form, I made notes on Acceleration Due to Gravity from AS which basically covers Galileo's experiment with the ball on the inclined slope.
    Speaking of Galileo, here is something incredibly cringy that I found at the bottom of my revision guide...
    Name:  ImageUploadedByStudent Room1474579631.827127.jpg
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    "Galileo" geezer.... Woooooow....


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    Hi,
    Firstly well done on not giving up and choosing to carry on. Im sure with hard work you will achieve a really good grade this year. I will be watching this thread and seek help, because Im also doing AQA A Level physics and in year 13.

    Also why didnt you start with centripetal force and acceleration?
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    Hey Guys I managed a B in AS physics but really need to boost this up to an A this year. I need to do well in my next two tests as our predicted grades will be confirmed in about 2 weeks. The tests should be on 1.simple harmonic motion and 2.nuclear physics. If anyone could help advice for them I'd appreciate it. Also, I've just looked into buying the aqa physics exampro thing on their website and wondered if anyone else had and if it would be that helpful. It's also £100 so I want to if it's really that useful and worth the money?

    Cheers
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    Good luck!
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    May I ask if you revise everyday? and for how long?
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    (Original post by KINGYusuf)
    May I ask if you revise everyday? and for how long?
    I try my best to spend a bit of time on physics every day. I don't really set myself time limits but I'll aim to cover a double page spread of my revision guide each day and that usually takes me about an hour, including answering the practice questions as well. That's just for the AS content though. For the A2 content, I usually just consolidate what we've done in class.

    (Original post by 10moorej)
    Hey Guys I managed a B in AS physics but really need to boost this up to an A this year. I need to do well in my next two tests as our predicted grades will be confirmed in about 2 weeks. The tests should be on 1.simple harmonic motion and 2.nuclear physics. If anyone could help advice for them I'd appreciate it. Also, I've just looked into buying the aqa physics exampro thing on their website and wondered if anyone else had and if it would be that helpful. It's also £100 so I want to if it's really that useful and worth the money?

    Cheers
    Hey! Congratulations on getting a B last year- that is still really good! For simple harmonic motion, I'd recommend practicing using the equations by answering questions from the textbook (if you have one) so that you know when and how to use them.
    I've haven't done nuclear physics yet but I assume it's less maths-heavy so perhaps making flashcards and/or mind maps could be helpful?
    Good luck!

    (Original post by asinghj)
    Hi,
    Firstly well done on not giving up and choosing to carry on. Im sure with hard work you will achieve a really good grade this year. I will be watching this thread and seek help, because Im also doing AQA A Level physics and in year 13.

    Also why didnt you start with centripetal force and acceleration?
    Hi, thank you for your kind words
    And by 'centripetal force and acceleration', do you mean the circular motion topic? If so, we covered that in class at the end of year 12.
    Also, we have two teachers who each teach us different topics. At the moment, one is teaching us further mechanics (including circular motion) and the other is teaching gravitational fields.
    Best of luck with your studies, and stay tuned to this thread haha!
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    24/09/16


    I forgot to post yesterday but in double physics, we answered questions from the textbook on simple harmonic motion and a miracle happened:
    when the teacher read out the answers at the end, most of my answers were correct!
    Usually in physics, the teacher is like "Okay, the answer to question one is 75 m" and then my answer is something ridiculous like 2.63 x 1011 :o:o. But I actually seemed to know what I was doing this time!

    Today I went to the open day at Loughborough University and it was really nice! I could only stay for the morning though because my dad (aka my taxi service) wanted to be home in the afternoon so that he could watch the football. Nice.
    When I got home, I made some psychology notes, made some AS physics notes on projectile motion and then completed an exercise on vertical motion from my M1 textbook. I was also going to do some C3 trig but I cba so I'll just do it tomorrow.
    Something strange/confusing I've noticed is that in physics, the downwards direction for g is usually negative ( -9.81) and the upwards direction is positive (+9.81), but in M1 it is the other way round. I'm confuzzled.
    Also, I know people say that you can choose which direction is positive or negative but I don't really think you can because the mark scheme only uses one way?! :confused: :dontknow:
    On the plus side, I got 6/7 marks on the projectile motion past exam questions that I did Dropped the last mark because I forgot that the object was projected from a point 1 meter above the ground so I didn't add this on to my final answer.
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    (Original post by jessyjellytot14)
    24/09/16


    I forgot to post yesterday but in double physics, we answered questions from the textbook on simple harmonic motion and a miracle happened:
    when the teacher read out the answers at the end, most of my answers were correct!
    Usually in physics, the teacher is like "Okay, the answer to question one is 75 m" and then my answer is something ridiculous like 2.63 x 1011 :o:o. But I actually seemed to know what I was doing this time!

    Today I went to the open day at Loughborough University and it was really nice! I could only stay for the morning though because my dad (aka my taxi service) wanted to be home in the afternoon so that he could watch the football. Nice.
    When I got home, I made some psychology notes, made some AS physics notes on projectile motion and then completed an exercise on vertical motion from my M1 textbook. I was also going to do some C3 trig but I cba so I'll just do it tomorrow.
    Something strange/confusing I've noticed is that in physics, the downwards direction for g is usually negative ( -9.81) and the upwards direction is positive (+9.81), but in M1 it is the other way round. I'm confuzzled.
    Also, I know people say that you can choose which direction is positive or negative but I don't really think you can because the mark scheme only uses one way?! :confused: :dontknow:
    On the plus side, I got 6/7 marks on the projectile motion past exam questions that I did Dropped the last mark because I forgot that the object was projected from a point 1 meter above the ground so I didn't add this on to my final answer.
    Your dad is a savage
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    (Original post by jessyjellytot14)
    Yeah I'm doing AQA for psychology!
    And same... I don't know what I got in each of the physics papers but I wouldn't be surprised if I got an A/B in paper 1 and a U in paper 2 tbh.
    I got As in both maths and psychology.. the D in physics looks so out of place and dodgy lmao. I'm hoping that my physics teachers predict me a B though.
    interesting lol, so what you going to study at uni?
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    (Original post by jessyjellytot14)
    Hi, thank you for your kind words
    And by 'centripetal force and acceleration', do you mean the circular motion topic? If so, we covered that in class at the end of year 12.
    Also, we have two teachers who each teach us different topics. At the moment, one is teaching us further mechanics (including circular motion) and the other is teaching gravitational fields.
    Best of luck with your studies, and stay tuned to this thread haha!
    Yea, that's it, we started this year with circular motion... Ana wow, I wish I had 2 teachers.. My teacher sucks and therefore I have to teach everything to myself, but I 'couldn't be bothered', so I am planning to start from monday .

    And wow, gravitational fields must be so exiting.. Can't wait until we start that

    And I will be tuned to this thread and read what you've been up to, to get me motivated hahaa
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    (Original post by Mysteryman95)
    interesting lol, so what you going to study at uni?
    Probably psychology. Although I've recently been considering meteorology... idk!

    (Original post by asinghj)
    Yea, that's it, we started this year with circular motion... Ana wow, I wish I had 2 teachers.. My teacher sucks and therefore I have to teach everything to myself, but I 'couldn't be bothered', so I am planning to start from monday .

    And wow, gravitational fields must be so exiting.. Can't wait until we start that

    And I will be tuned to this thread and read what you've been up to, to get me motivated hahaa
    Haha I usually end up teaching everything to myself even if my teacher is really good because I forget stuff easily
    And gravitational fields is sort of interesting but I'm looking forward to doing thermodynamics and nuclear physics!
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    25/09/16



    Existential crisis...

    Okay, so I was revising Newton's three laws of motion when I suddenly saw the most beautiful cumulonimbus cloud out of my window and it made me have an epiphany: maybe I could/should study meteorology at university instead of psychology? I find psychology really interesting but I think i'll enjoy being a meteorologist more than I would being a psychologist. I'm also really starting to get into maths (and even enjoying physics more!) and I've always had an interest in the weather and its patterns.
    The only problem is that I'm not very likely to be predicted a B in physics this year and I haven't done much (any) extra reading/research on meteorology because I've wanted to be a psychologist for the past couple of years...
    I don't know wtf I want to do with my life!!

    Update: I think i'll just stick with psychology because the physics will probably overwhelm my brain lmao.
 
 
 
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