Hey there! Sign in to join this conversationNew here? Join for free
    Offline

    0
    ReputationRep:
    (Original post by Felix Felicis)
    Haven't you heard how rowdy mathematicians can get? :confused:
    LOL

    (Original post by thers)
    Seems like lots of ppl posting on this thread have lots of warning points... Wonder why.. :confused:
    Well, sometimes when trying to prove something is rational, you have to start acting and thinking a lil' irrational
    Spoiler:
    Show
    Thing get crazy in here


    (Original post by Boy_wonder_95)
    Yh 8c I believe it was, I thought something similar; that the vertical velocity would be the same but in the opposite direction but I got it all wrong. Still managed a method mark for using v = u + at :lol:
    Gotta love the method marks you get for certain things eh?
    +1 for writing +c in c1 integration LOL

    Seriously though, this thread has some rebellious mathematicians
    Offline

    15
    ReputationRep:
    (Original post by MathsNerd1)
    That's fair enough then and that would've been the only place I dropped marks too, however I put the correct answer for the impulse question but then decided to cross it out as I actually thought it wouldn't make much sense of the direction afterwards if it got hit at that angle, so I lost a good amount of marks there but still got 65/75 in the end which wasn't all that bad considering the grade boundaries
    67/75 for 100 UMS! :teeth: I wouldn't mind something like that for the real thing , the impulse question seemed scary at first but once you resolved it it was fine and seeing the modulus in COM was like :zomg:... but it made sense at the end since you can't have negative distance, apart from those 3 questions it was a standard paper :dontknow:.
    Offline

    11
    ReputationRep:
    (Original post by tigerz)
    LOOL good luck I told you i'd find a good question
    Felix here:
    There is a rabbit that runs in a perfect circle of radius r with a constant speed v. A fox chases the rabbit, starting from the center of the circle and also moves with a constant speed v such that it is always between the center of the circle and the rabbit. How long will it take for the fox to catch the rabbit?
    I can't seem to form a suitable equation for the components of v.
    Spoiler:
    Show
    I've got
    Rabbit:
    R(t) = r

\theta = \dfrac{vt}{r}

    And for the fox, the angle is the same, and I think one of the components of the velocity is
    r\dfrac{d\theta}{dt}

\Rightarrow v^2 = (SOMETHING)^2 + r^2\left(\dfrac{d\theta}{dt} \right)^2
    But I can't get hold of the other.
    I suspect that there's a formula for it but I don't know it.
    Also I suspect that DJ could come up with some relative motion solution but I can't
    Offline

    15
    ReputationRep:
    (Original post by tigerz)
    Gotta love the method marks you get for certain things eh?

    Seriously though, this thread has some rebellious mathematicians
    Nah , it would be annoying if you lost method marks yet ended with the correct answer :getmecoat:
    • Study Helper
    Offline

    3
    ReputationRep:
    Study Helper
    (Original post by Boy_wonder_95)
    67/75 for 100 UMS! :teeth: I wouldn't mind something like that for the real thing , the impulse question seemed scary at first but once you resolved it it was fine and seeing the modulus in COM was like :zomg:... but it made sense at the end since you can't have negative distance, apart from those 3 questions it was a standard paper :dontknow:.
    That marks for 100 UMS would be just lovely in the real thing And yeah that's what I did at first but then I started to act it out with my arms and it literally didn't seem possible so I went down the other route which just happened to be incorrect :mad: I also got horrified by the modulus sign in COM and just thought I'll be getting about 40/75 for this paper but like you said it all made sense at the end, however I missed out a factor in the process so had to pick through my method to find the mistake to correct it which took a good 10 minutes!

    Yeah it wasn't as bad after doing them all, however I wouldn't have liked that in the actual exam, neither would I like June 2012 with the COM question in that one too!

    I feel those 2 were the hardest really.
    Offline

    0
    ReputationRep:
    (Original post by Boy_wonder_95)
    Nah , it would be annoying if you lost method marks yet ended with the correct answer :getmecoat:
    Lol true, that happens with me in C2, so this time I showed every lil' step lool
    Its good when you don't know what to do or make a silly mistake
    Offline

    1
    ReputationRep:
    (Original post by justinawe)
    I went through one of those papers... they are pretty weird, I had no idea MEI made such papers.

    I'm not sure if you can actually revise for it, seems more like a test of mathematical thinking/logic if you get me. Maybe do some past papers for familiarisation but other than that I'm not too sure what you can do.
    OK, I'll just go through each past paper so I can feel more familiar with it. Thanks
    Offline

    0
    ReputationRep:
    (Original post by joostan)
    I can't seem to form a suitable equation for the components of v.
    Spoiler:
    Show
    I've got
    Rabbit:
    R(t) = r

\theta = \dfrac{Vt}{r}

    And for the fox, the angle is the same, and I think one of the components of the velocity is
    r\dfrac{d\theta}{dt}

\Rightarrow v^2 = (SOMETHING)^2 + r^2\left(\dfrac{d\theta}{dt} \right)^2
    But I can't get hold of the other.
    I suspect that there's a formula for it but I don't know it.
    Also I suspect that DJ could come up with some relative motion solution but I can't
    Defo on the right track!
    The first two lines are perfect try forming a full a differential equation?
    If \theta=\frac{Vt}{r} what is \theta'?
    Also, remember v is constant...If you want a hint let me know
    Offline

    11
    ReputationRep:
    (Original post by tigerz)
    Defo on the right track!
    The first two lines are perfect try forming a full a differential equation?
    If \theta=\frac{Vt}{r} what is \theta'?
    That's not a problem.
    \theta' = \dfrac{d\theta}{dt} = \dfrac{v}{r}
    The issue is I can't get hold of an expression for either:
    \dfrac{dr}{dt} \ \mathrm{or} \ \dfrac{dr}{d\theta}
    This'd allow me to form and solve a differential equation (hopefully seperable ) of the form:
    t = \displaystyle\int^R_0 f(r) \ dr
    Offline

    0
    ReputationRep:
    (Original post by joostan)
    That's not a problem.
    \theta' = \dfrac{d\theta}{dt} = \dfrac{v}{r}
    The issue is I can't get hold of an expression for either:
    \dfrac{dr}{dt} \ \mathrm{Or} \ \dfrac{dr}{d\theta}
    This'd allow me to form and solve a differential equation (hopefully seperable ) of the form:
    t = \displaystyle\int^R_0 f(r) \ dr
    Ahh I see, does this help ?
    For this problem it is advisable to introduce polar coordinates (r and ϕ). The rabbit runs at speed v on a perfect circle with radius R. Therefore, ϕ=vt/R (you know all of this)
    As the fox stays between the center and the rabbit, it is at the same ϕ. The fox's speed (which is constant) has two component (prime denotes the derivative with respect to time)
    this means...

    v=\sqrt{something^2+something^2 \theta'^2}
    Offline

    11
    ReputationRep:
    (Original post by tigerz)
    Ahh I see, does this help ?
    For this problem it is advisable to introduce polar coordinates (r and ϕ). The rabbit runs at speed v on a perfect circle with radius R. Therefore, ϕ=vt/R (you know all of this)
    As the fox stays between the center and the rabbit, it is at the same ϕ. The fox's speed (which is constant) has two component (prime denotes the derivative with respect to time)
    this means...

    v=\sqrt{something^2+something^2 \theta'^2}
    I know that:
    v=\sqrt{(SOMETHING)^2 + r^2\left(\dfrac{d\theta}{dt} \right)^2}
    I said so in the last post, the other something is what I cannot derive
    Offline

    15
    ReputationRep:
    (Original post by MathsNerd1)
    That marks for 100 UMS would be just lovely in the real thing And yeah that's what I did at first but then I started to act it out with my arms and it literally didn't seem possible so I went down the other route which just happened to be incorrect :mad: I also got horrified by the modulus sign in COM and just thought I'll be getting about 40/75 for this paper but like you said it all made sense at the end, however I missed out a factor in the process so had to pick through my method to find the mistake to correct it which took a good 10 minutes!

    Yeah it wasn't as bad after doing them all, however I wouldn't have liked that in the actual exam, neither would I like June 2012 with the COM question in that one too!

    I feel those 2 were the hardest really.
    I haven't tried June 2012 yet so I can't comment, yet I've had a quick look and that impulse and COM question do look kind of spooky! I've still got quite a few papers to do
    Offline

    15
    ReputationRep:
    (Original post by joostan)
    I can't seem to form a suitable equation for the components of v.
    Spoiler:
    Show
    I've got
    Rabbit:
    R(t) = r

\theta = \dfrac{vt}{r}

    And for the fox, the angle is the same, and I think one of the components of the velocity is
    r\dfrac{d\theta}{dt}

\Rightarrow v^2 = (SOMETHING)^2 + r^2\left(\dfrac{d\theta}{dt} \right)^2
    But I can't get hold of the other.
    I suspect that there's a formula for it but I don't know it.
    Also I suspect that DJ could come up with some relative motion solution but I can't
    You started M3 already?

    (Original post by tigerz)
    Lol true, that happens with me in C2, so this time I showed every lil' step lool
    Its good when you don't know what to do or make a silly mistake
    I went at a snails pace throughout the C2 exam, there was no way I was gonna make a silly mistake this time
    Offline

    1
    ReputationRep:
    (Original post by Boy_wonder_95)
    Did M2 Jan 2010 for the first time and got 70 , I wouldn't say it's that bad although my method for quite a few was different to the MS. Dropped all the marks on the last question as I didn't know what to do. I mean why did they use dy/dx for projectiles?
    I haven't seen the question but I'm going to assume they used it to find the maximum height of the path of trajectory (or something along those lines).
    Offline

    11
    ReputationRep:
    (Original post by Boy_wonder_95)
    You started M3 already?
    No. tigerz found a problem on the internet, I had a peek at the wikipedia page on circular motion, but I can't find the second component
    • Study Helper
    Offline

    3
    ReputationRep:
    Study Helper
    (Original post by Boy_wonder_95)
    I haven't tried June 2012 yet so I can't comment, yet I've had a quick look and that impulse and COM question do look kind of spooky! I've still got quite a few papers to do
    Let me know how you get on with it and hopefully you'll be able to explain to me on how to do the COM question, only the second part though as I can do the first part, also the impulse question isn't that bad once you've got it straight in your mind
    Offline

    0
    ReputationRep:
    (Original post by joostan)
    I know that:
    v=\sqrt{(SOMETHING)^2 + r^2\left(\dfrac{d\theta}{dt} \right)^2}
    I said so in the last post, the other something is what I cannot derive
    Oh yeah, my bad x_x I need to learn how to read.
    Right you have information about 3 things, this 'something squared' is one of these intitials...tbh this is the only difficult part, after you can derive this the questions average

    (Original post by Boy_wonder_95)
    You started M3 already?

    I went at a snails pace throughout the C2 exam, there was no way I was gonna make a silly mistake this time
    Haha, I always manage to make silly mistakes :s But it weren't to bad in cores, in S1 I got all the difficult bits right and messed up easy bits because of silly mistakes >.<
    Offline

    11
    ReputationRep:
    (Original post by tigerz)
    Oh yeah, my bad x_x I need to learn how to read.
    Right you have information about 3 things, this 'something squared' is one of these intitials...tbh this is the only difficult part, after you can derive this the questions average
    The number of days of me knowing anything about circular motion = \lim{x \to 0}\left(\dfrac{\sin(x)}{x} \right)
    Allow me to be the judge of that
    Offline

    15
    ReputationRep:
    (Original post by ThatRandomGuy)
    I haven't seen the question but I'm going to assume they used it to find the maximum height of the path of trajectory (or something along those lines).
    Nah, the question asked to find the vertical component of the velocity when it's travelling at right angles to it's initial velocity.

    Name:  Projectiles.png
Views: 51
Size:  15.0 KB

    Full question is here, part c)
    Offline

    1
    ReputationRep:
    (Original post by Boy_wonder_95)
    Nah, the question asked to find the vertical component of the velocity when it's travelling at right angles to it's initial velocity.

    Name:  Projectiles.png
Views: 51
Size:  15.0 KB

    Full question is here, part c)
    Ohhh you're talking of that paper...

    Spoiler:
    Show
    If I remember correctly I got 72/75 when I did that paper. Dropped marks on the impulse question. I say more A level papers need to be like this one
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Brussels sprouts
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.