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    for Q 7 the formula for transformers is;
    Vp/Vs = Np/Ns (Vp=voltage of primary, Vs= " of secondary, Np = no. of turns on primary, Ns = " 2ndry)

    put in the values you know

    250/Vs = 1500/Ns
    you're give that for the secondary transformer, current = 10A, and power = 500W
    use the formula P = IV, reaarange to V=P/I
    find the voltage, put it back in the formula at the start and solve it to find the Ns.
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    (Original post by Isometrix)
    for Q 7 the formula for transformers is;
    Vp/Vs = Np/Ns (Vp=voltage of primary, Vs= " of secondary, Np = no. of turns on primary, Ns = " 2ndry)

    put in the values you know

    250/Vs = 1500/Ns
    you're give that for the secondary transformer, current = 10A, and power = 500W
    use the formula P = IV, reaarange to V=P/I
    find the voltage, put it back in the formula at the start and solve it to find the Ns.
    iso got any idea how to solve that box plot one?

    i know the 'box' represents 50% of where all the values lie. Therefore, 1/4 of members did between 800-850 steps whilst 3/4 did 850-1100. But what i do from there
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    (Original post by Isometrix)
    for Q 7 the formula for transformers is;
    Vp/Vs = Np/Ns (Vp=voltage of primary, Vs= " of secondary, Np = no. of turns on primary, Ns = " 2ndry)

    put in the values you know

    250/Vs = 1500/Ns
    you're give that for the secondary transformer, current = 10A, and power = 500W
    use the formula P = IV, reaarange to V=P/I
    find the voltage, put it back in the formula at the start and solve it to find the Ns.
    Oh my gosh! You are amazing! I never understood anything like that before, but it clicks. I figures out the P=IV bit, but I didn't understand the rest. Thank you sooo much!

    Muni.
    xx
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    (Original post by DaveJ)
    NUMBER 19:

    Remember, uniform bar, weight acts in centre.

    Moments clockwise = moments anticlockwise

    Take moments about the pivot:

    (1.5)(1000) = (4.5)(100) + 1.5w


    Solve to get 700.
    Thank you!

    I kept doing: (1.5)(1000) = (4.5)(100) + 4.5w


    Muni.
    xx
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    AHHHHH. how do you manage to do bmat in the crazy short times?? its impossible? i mean is it just me being a slow coach or what?
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    (Original post by *fran1991*)
    AHHHHH. how do you manage to do bmat in the crazy short times?? its impossible? i mean is it just me being a slow coach or what?

    Don't worry. I go over the time too.
    Although, the first time I was on msn...
    I needed 7 extra minutes on the second one I did on unit two.
    What scores are you getting?
    I got 4. something on my first go and 6.2 on my second... Getting there. :P:

    If we finish unit one or unit three early, will we be able to go back to unit two. Or is that out of the question?

    Muni.
    xx
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    (Original post by munim)
    Don't worry. I go over the time too.
    Although, the first time I was on msn...
    I needed 7 extra minutes on the second one I did on unit two.
    What scores are you getting?
    I got 4. something on my first go and 6.2 on my second... Getting there. :P:

    If we finish unit one or unit three early, will we be able to go back to unit two. Or is that out of the question?

    Muni.
    xx
    nope. You sit one at a time. 1 hour over...section 1 over, 30 mins over...section 2 over. Not allowed to return to other sections!
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    (Original post by motiv3)
    iso got any idea how to solve that box plot one?

    i know the 'box' represents 50% of where all the values lie. Therefore, 1/4 of members did between 800-850 steps whilst 3/4 did 850-1100. But what i do from there
    i haven't a clue. could someone explain how to do it ?
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    (Original post by motiv3)
    nope. You sit one at a time. 1 hour over...section 1 over, 30 mins over...section 2 over. Not allowed to return to other sections!
    Darn! It's like a real exam. Thanks for letting me know.

    Muni.
    xx
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    I do okay..when i go at my pace. so i dont know whether to go slow and be more sure of getting them right but have to guess lots at the end, or speed up and take less care? sooooo any speeding up tips people? mainly section 2.
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    (Original post by Isometrix)
    i haven't a clue. could someone explain how to do it ?

    I keep trying and failing epicly.

    The chance is between the median and upper quartile, so that's a quarter of the 30 people.

    I'd have assumed it was:

    (7.5/30)*(6.5/29)*(5.5/28)

    but that's not the correct answer
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    (Original post by DaveJ)
    NUMBER 19:

    Remember, uniform bar, weight acts in centre.

    Moments clockwise = moments anticlockwise

    Take moments about the pivot:

    (1.5)(1000) = (4.5)(100) + 1.5w
    why is it 1.5w?:confused:
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    (Original post by Aiex)
    why is it 1.5w?:confused:

    Bar is 6m long, weight acts 3m from each end.

    Pivot is 1.5m from left end, so weight acts 1.5m from the pivot.
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    (Original post by Aiex)
    why is it 1.5w?:confused:

    The center off mass is the center of the plank i.e 3 meters.

    so the force W is 1.5 meters from the pivot.

    Moment = force * distance form pivot.
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    (Original post by DaveJ)
    Bar is 6m long, weight acts 3m from each end.

    Pivot is 1.5m from left end, so weight acts 1.5m from the pivot.
    aah i see, thanks DaveJ and Jjkkll
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    box plot question: (1/4)^3=1/64
    upper quart minus median is 1/4 of data.you multiply as these 3 people are independent of each other.
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    (Original post by Mr Halpert)
    upper quart minus median is 1/4 of data.
    is that a general rule, or did you have to work that out somehow?
    my stats sucks
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    (Original post by Mr Halpert)
    box plot question: (1/4)^3=1/64
    upper quart minus median is 1/4 of data.you multiply as these 3 people are independent of each other.
    Hmmm... I thought you would have to find one quarter of 30. Can you explain why you don't have to do that?
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    (Original post by Mr Halpert)
    box plot question: (1/4)^3=1/64
    upper quart minus median is 1/4 of data.you multiply as these 3 people are independent of each other.
    Darn! I just worked it out too! :P

    Muni.
    xx
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    (Original post by Isometrix)
    is that a general rule, or did you have to work that out somehow?
    my stats sucks

    General, cos upper quartile is 3/4 of way through data, and median is half way through data. 3/4 minus 1/2 = 1/4
 
 
 
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