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    I am really confused with q5 on this paper, I've tried approaching the question with vectors and for part a worked out:

    mom before: 0.25(30i) = 7.5i
    mom after: 0.25v

    but not sure how to get an answer from there, and am clueless with part b

    would appreciate some advice on how to tackle this thanks


    Question paper: https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

    mark scheme: https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf
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    (Original post by Katiee224)
    I am really confused with q5 on this paper, I've tried approaching the question with vectors and for part a worked out:

    mom before: 0.25(30i) = 7.5i
    mom after: 0.25v

    but not sure how to get an answer from there, and am clueless with part b

    would appreciate some advice on how to tackle this thanks


    Question paper: https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

    mark scheme: https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf
    Read this and was wondering why you were saying mum before and mum after. :rofl:

    Anyways, vectors is slightly awkward here, let's resolve instead (which is almost the same thing as vectors)

    If we consider only horizontal motion, we get:

    Impulse = change in momentum. The horizontal component of impulse is 12.5 sin \alpha pointing to the left.

    The speed of B horizontally is (let's say v):

    The 12.5\sin \alpha = 0.25v - 0.25(-30) where we use - since the ball is moving 30 metres per second opposite to the impulse and we gave impulse a +12.5 sinalpha.

    Anyways, since \sin \alpha = 0.6 we have: 12.5(0.6) = 0.25v + 7.5 \iff 7.5 = 0.25v + 7.5, this gives v=0.

    So there is no horizontal component of B, thank god, that makes life simple!

    Now - let's consider vertical motion:

    This gives us: 12.5\cos \alpha (impulse acts upwards)

    And the change in momentum is 0.25u - 0 (u is our vertical speed) and there is no vertical motion previous to the impulse.

    So 12.5\cos \alpha = 0.25u \iff u = 4\times 12.5 \times 0.8 = 40. So the speed is 40 vertical and 0 horizontal, and hence 40 overall.

    And from this, since the 40 overall is acting vertically upwards, then the direction of travel of B is "perpendicular to the original direction". i.e: it went from pure horizontal to pure vertical.
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    (Original post by Zacken)
    Read this and was wondering why you were saying mum before and mum after. :rofl:

    Anyways, vectors is slightly awkward here, let's resolve instead (which is almost the same thing as vectors)

    If we consider only horizontal motion, we get:

    Impulse = change in momentum. The horizontal component of impulse is 12.5 sin \alpha pointing to the left.

    The speed of B horizontally is (let's say v):

    The 12.5\sin \alpha = 0.25v - 0.25(-30) where we use - since the ball is moving 30 metres per second opposite to the impulse and we gave impulse a +12.5 sinalpha.

    Anyways, since \sin \alpha = 0.6 we have: 12.5(0.6) = 0.25v + 7.5 \iff 7.5 = 0.25v + 7.5, this gives v=0.

    So there is no horizontal component of B, thank god, that makes life simple!

    Now - let's consider vertical motion:

    This gives us: 12.5\cos \alpha (impulse acts upwards)

    And the change in momentum is 0.25u - 0 (u is our vertical speed) and there is no vertical motion previous to the impulse.

    So 12.5\cos \alpha = 0.25u \iff u = 4\times 12.5 \times 0.8 = 40. So the speed is 40 vertical and 0 horizontal, and hence 40 overall.

    And from this, since the 40 overall is acting vertically upwards, then the direction of travel of B is "perpendicular to the original direction". i.e: it went from pure horizontal to pure vertical.
    thanksss so much, your explanation was really helpful, i understand it all now! can you be my personal maths tutor please :laugh:

    how come you are always so quick to reply to my problems hehe :blushing:
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    (Original post by Katiee224)
    thanksss so much, your explanation was really helpful, i understand it all now! can you be my personal maths tutor please :laugh:

    how come you are always so quick to reply to my problems hehe :blushing:
    Oh, phew! Glad it makes sense.

    It's 'cause I'm secretly madly in love with you. :laugh:
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    (Original post by Katiee224)
    thanksss so much, your explanation was really helpful, i understand it all now! can you be my personal maths tutor please :laugh:

    how come you are always so quick to reply to my problems hehe :blushing:
    27 minute turn around is slow for him loool. He just likes helping people and his latex skills are unmatched
 
 
 
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