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***JC 2014 Technology Papers - Wed. June 18th 2014 - all levels***

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  • 17-06-2014 9:30am
    #1
    coolerboy
    Registered Users Posts: 589 ✭✭✭


    Technology (OL and HL)
    Wednesday June 18th 2014




    All discussion and questions about Technology papers goes here, following the exam. Please do not post predictions or discussion here before the exam.

    Usual rules apply. Anyone slagging off another poster about the level they did, or a mistake they made, will be banned for the duration of the exams.

    Please keep off-topic chat elsewhere.

    Good luck all.


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    #2
    spurious
    Moderators, Category Moderators, Education Moderators Posts: 27,188 CMod ✭✭✭✭spurious


    Bumping to bring it up to the top of the page


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    #3
    coolerboy
    Registered Users Posts: 589 ✭✭✭coolerboy


    Does anyone here do technology. If u do what u get for the mechanisms question caluation I got 1 minute but I think it was 45 seconds


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    #4
    nanook5
    Registered Users Posts: 927 ✭✭✭nanook5


    coolerboy wrote: »
    Does anyone here do technology. If u do what u get for the mechanisms question caluation I got 1 minute but I think it was 45 seconds

    I do it but I did electronics :P


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    #5
    danm14
    Registered Users Posts: 218 ✭✭danm14


    The one with the how long the motor takes to move 30mm? 6 seconds I got. I'd be fairly sure you're wrong I'm afraid because it wouldn't be that likely itd take a minute to move something just over an inch :P Still of course it's an exam, not real life so it's possible I'm wrong and you're right!

    Did you do Q6 (Control Systems)? If so what was the logic gate A? I said a NOT gate, because it was the only one with one input, but it didn't seem like it would work.
    Our teacher told us not to do that question but I did every past control systems question back till 2001 and corrected with the mark scheme and got full marks, so I'm not sure of the answers - we were never taught it, it just made sense to me immediately.

    Did everyone in your exam leave early today? By the time the exam was over in my centre, everyone bar myself and one other lad had left about fifteen minutes early, even a person who gets extra time to finish as a reasonable accomodation. Whether that was because it was their last exam or because they were genuinely finished early I don't know, but I'd be assuming the former :P


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    #6
    danm14
    Registered Users Posts: 218 ✭✭danm14


    Motor spins at 150RPM (rotations per minute)
    Attached to worm (1 tooth per rotation)
    Worm spins at 150RPM
    Attached to worm wheel (20 teeth)
    Wheel spins at 7.5RPM (150/20=7.5)
    15 teeth = 30mm
    15 teeth / 7.5 RPM = 2

    I get 2 minutes now.... Where I got 6 seconds from I don't know!
    If someone who understands gear calculations could do this out:

    Motor @ 150RPM with worm.
    Worm attached to Worm wheel 20 teeth
    Worm wheel acts as Pinion attached to Rack - 5 teeth = 10mm
    How long for the rack to move 30mm?

    2014 Technology Section B Question 2(b), specifically part (iii)


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    #7
    coolerboy
    Registered Users Posts: 589 ✭✭✭coolerboy


    150÷10=15
    Moves 1teeth every rotation
    10mm=5 teeth
    30mm=15 teeth
    1 minute


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    #8
    danm14
    Registered Users Posts: 218 ✭✭danm14


    coolerboy wrote: »
    150÷10=15
    Moves 1teeth every rotation
    10mm=5 teeth
    30mm=15 teeth
    1 minute

    Why are you dividing by 10?
    I see it now as: 150 teeth per minute on the worm wheel = 150 teeth per minute on the rack
    150teeth/15teeth = 10 teeth
    60sec/10sec = 6sec


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    #9
    coolerboy
    Registered Users Posts: 589 ✭✭✭coolerboy


    danm14 wrote: »
    Why are you dividing by 10?
    I see it now as: 150 teeth per minute on the worm wheel = 150 teeth per minute on the rack
    150teeth/15teeth = 10 teeth
    60sec/10sec = 6sec

    Worm wheel reduces speed by 10


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    #10
    danm14
    Registered Users Posts: 218 ✭✭danm14


    coolerboy wrote: »
    Worm wheel reduces speed by 10

    That is wrong, it would depend on the number of teeth on the worm wheel how much the speed would be reduced. (In this case it's reduced by 7.5 however that is irrelevant here)

    For every one rotation of the motor, one tooth on the worm wheel moves.

    In sixty seconds, 150 teeth on the worm wheel move. This means that in 6 seconds, 15 teeth move. This moves the rack by 15 teeth (30mm)


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    #11
    coolerboy
    Registered Users Posts: 589 ✭✭✭coolerboy


    danm14 wrote: »
    That is wrong, it would depend on the number of teeth on the worm wheel how much the speed would be reduced. (In this case it's reduced by 7.5 however that is irrelevant here)

    For every one rotation of the motor, one tooth on the worm wheel moves.

    In sixty seconds, 150 teeth on the worm wheel move. This means that in 6 seconds, 15 teeth move. This moves the rack by 15 teeth (30mm)

    Ok ok ok i get it know.........




    (Sarcastically)


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