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    (Original post by hadtosignup)
    Yes, here it is (according to what you have labelled as Q7 on the first page):

    If the initial velocity is 3i - 22j and the acceleration is 3i + 9j, find the speed when t = 3s.


    For the section where we are asked the velocities of P and Q as a function of time, I remember it was something like this:
    P moves with velocity 15i + 20j and Q moves with velocity 20i-5j. At t = 0, P has position vector 400i and Q has position vector 800i. Find an expression for the position vectors of P and Q at time t.
    ok ive done this twice now (once in the exam, once again now) and ive got the same answer which is different to what I have been seeing.

    V= U + AT
    V = ? U = (3i-22j) A=(3i+9j) T=3
    |U| = root(3^2 + (-22)^2) = root(493)
    |A| = root(3^2 + 9^2) = root(90)

    V = root(493) + 3*root(90)

    V= 50.66410225
    V = 50.7


    anyone?
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    (Original post by spnislife)
    Lower than 59 last year? I think I got 61ish, do you think that's enough to get me an A?
    Not sure how low, but I wouldn't worry about it, you grade will be an average over 3 modules so focus on your final module if you still have it
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    How many marks would I get for this for question 2 (b) (it was out of 3 marks)


    Resolve upwards for the sauce pan

    R - 1.5g - 0.5g = 0.5a
    R = 1.5g + 0.5 + 0.5(0.5)
    R = 19.9 N

    Could I possibly get atleast 1 M1 Method marks out of the 3?
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    (Original post by KloppOClock)
    ok ive done this twice now (once in the exam, once again now) and ive got the same answer which is different to what I have been seeing.

    V= U + AT
    V = ? U = (3i-22j) A=(3i+9j) T=3
    |U| = root(3^2 + (-22)^2) = root(493)
    |A| = root(3^2 + 9^2) = root(90)

    V = root(493) + 3*root(90)

    V= 50.66410225
    V = 50.7


    anyone?
    I did:
    v=u+at (in vector form):
    v = 3i - 22j +3(3i + 9j)
    v = 3i - 22j +9i + 27j
    v = 12i + 5j

    => speed = root(12^2 + 5^2) = root(169) = 13
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    (Original post by KloppOClock)
    ok ive done this twice now (once in the exam, once again now) and ive got the same answer which is different to what I have been seeing.

    V= U + AT
    V = ? U = (3i-22j) A=(3i+9j) T=3
    |U| = root(3^2 + (-22)^2) = root(493)
    |A| = root(3^2 + 9^2) = root(90)

    V = root(493) + 3*root(90)

    V= 50.66410225
    V = 50.7


    anyone?
    You have to answer in vectors first...as acceleration can be a change of direction so converting it to acceleration magnitude to soon gets you the wrong answer.... is did V=(2-22)+(3+9)t....then found the magnitude of the velocity from the vector for V
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    (Original post by KloppOClock)
    Not sure how low, but I wouldn't worry about it, you grade will be an average over 3 modules so focus on your final module if you still have it
    Hello, for question 3 I put 1.225 for acceleration but I was aware that it's actually a deceleration of -1.225 and I did get the correct answer. Do you think I'll lose one or two marks for that? All the other answers are the same as urS
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    (Original post by hadtosignup)
    I did:
    v=u+at (in vector form):
    v = 3i - 22j +3(3i + 9j)
    v = 3i - 22j +9i + 27j
    v = 12i + 5j

    => speed = root(12^2 + 5^2) = root(169) = 13
    that looks right but i dont know why its right, kinda pissed that i lost those marks now
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    (Original post by KloppOClock)
    Not sure how low, but I wouldn't worry about it, you grade will be an average over 3 modules so focus on your final module if you still have it
    I think I've done alright on C1 and C2, so fingers crossed for results day! Thanks.
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    (Original post by Andylauinfinity)
    Hello, for question 3 I put 1.225 for acceleration but I was aware that it's actually a deceleration of -1.225 and I did get the correct answer. Do you think I'll lose one or two marks for that? All the other answers are the same as urS
    not really, it depends on which way you took positive, if you got the right answer in the end I would think you would get all the marks
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    (Original post by KloppOClock)
    Not sure how low, but I wouldn't worry about it, you grade will be an average over 3 modules so focus on your final module if you still have it
    do you have pictures of a solution for 7a?? btw thank you for making this thread
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    (Original post by KloppOClock)
    that looks right but i dont know why its right, kinda pissed that i lost those marks now
    I'm sorry, it's always frustrating.
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    I got all the hard questions but messed up on the simple ones Arghhhhh ...I swear doing only gold papers isnt good, you get used to particular types of questions....then you misdraw a bloody velocity time graph or a moments question....my physics teacher would go mad if he knew.....need to smash C3+C4 now.....
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    Does anybody have the exact wording of question 2 about the brick, or have a picture of the question which they could send me please?
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    (Original post by Medlad101)
    do you have pictures of a solution for 7a?? btw thank you for making this thread
    sure let me just amend part b and il upload it, check back in a few mins.
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    (Original post by KloppOClock)
    sure let me just amend part b and il upload it, check back in a few mins.
    thank you! have you done Q2 as well?
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    Can someone post the paper?
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    (Original post by KloppOClock)
    that looks right but i dont know why its right, kinda pissed that i lost those marks now
    You work it out as a vector first, because if you change it into a speed first (like you did) you lose the 'directional' component of the vector. Therefore, by changing to a scalar quantity first, you don't take into account the difference in direction that it accelerates in. Sorry if this doesn't help at all.

    I know what you mean; I lost 4-5 from putting the numbers into my calculator wrong on the last question. Annoying after an otherwise good exam.
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    (Original post by KloppOClock)
    not really, it depends on which way you took positive, if you got the right answer in the end I would think you would get all the marks
    Thanks. Hopefully I'll get full mark
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    (Original post by 9899thft)
    Can someone post the paper?
    Yep need to see paper please^
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    (Original post by Medlad101)
    thank you! have you done Q2 as well?
    just need to do 2 and 8, but im missing parts of the question
 
 
 
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