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Mechanical apptitude to suggest the direction of action.

  1. Mar 12, 2012 #1
    hi ..
    1. The problem statement, all variables and given/known data

    we have this gear system (we put an equal weight W).where will the action like A or like B direction?

    http://data.imagup.com/11/1146214320.jpg

    thanks for you suggestion.
     
  2. jcsd
  3. Mar 12, 2012 #2

    tiny-tim

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    hi zizodev! :smile:

    what is the general principle to apply for the direction (clockwise or anti-clockwise) of connected gearwheels?
     
  4. Mar 12, 2012 #3
    i think it doesn't matter the direction..the same weight on the axes and what will happen. we have a tothed wheel gear (one bigger than the other)..
    for me i choose B.
     
  5. Mar 12, 2012 #4

    tiny-tim

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    the general principle is that if one gear goes clockwise, the next must go anticlockwise

    now apply that :smile:
     
  6. Mar 12, 2012 #5

    S_Happens

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    I believe his question is more gear ratios/mechanical advantage rather than whether the device can/will turn. The question as I see it is "if the same weights are placed on this device, what will be the direction of motion of each side (rack)?" The two answers provided are opposite of each other, so it's really only to determine which side goes down.

    To the OP- What is your reasoning for choosing B?
     
  7. Mar 13, 2012 #6
    NB:i have studied french. my english is too bad.
    yeas that's is S_Happens.
    "question is more gear ratios/mechanical advantage rather than whether the device can/will turn. The question is "if the same weights are placed on this device, what will be the direction of motion of each side (rack)?" The two answers provided are opposite of each other, so it's really only to determine which side goes down.

    To the OP- What is your reasoning for choosing B?
    because the radius of the big gear we can have a big force (momentum) and we know that the small gear (have less force and turn faster than the big gear).isn't it
     
  8. Mar 13, 2012 #7

    tiny-tim

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    hi zizodev! :smile:

    actually, now that i look at your diagram more carefully, the way you've drawn A and B makes them the same

    one should be two arrows in the same direction, the other should be two arrows in opposite directions! :wink:

    as i said, alternate gears go opposite ways, so pretend the two straight gears are parts of very large circles, one with its centre on the left, and one with its centre on the right …

    that gives you five circles! :smile:
     
  9. Mar 13, 2012 #8
    no tiny-tim...the direction of sliding of the ranks..
    choice A:the left rank will goes up the right one will goes down.
    choice B:the right rank will goes down the right one will goes up.

    and we have the same weight on the both ranks.
    so what choice A or B will be the correct one..and why??

    http://data.imagup.com/12/1146300036.jpg
     
  10. Mar 13, 2012 #9

    tiny-tim

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    but (if you've shown us the full question) the question doesn't tell you which way either of them goes …

    so it's only asking: do they go the same way or opposite ways?
     
  11. Mar 13, 2012 #10

    S_Happens

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    The reason I posted is because I interpreted your post to see the question this way, while that was not the actual question being asked.

    The original question that was posted gave two options
    A) right side goes up while left side goes down
    B) right side goes down while left side goes up

    There was no option for both going the same way, which is why I pointed out that it's a question about gear ratios/mechanical advantage rather than simply which way gears can turn. Obviously there is one larger gear and two smaller gears with similar racks and weights.

    To be clear, tiny-tim you are misunderstanding the question.

    To the OP- Yes, your reasoning is correct. Momentum is not the correct term. Just consider the torques applied to each gear by the racks (straight gears). The larger radius gear wheel allows a longer lever arm, which means more torque.
     
  12. Mar 16, 2012 #11
    yes mr:S_Happens ...this is the solution as i have suggested."The larger radius gear wheel allows a longer lever arm, which means more torque." :) thnks brothers.
     
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