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Chopping wood - torque question

  1. Jan 24, 2010 #1
    So, I was just chopping the wood, and the way I do it is this : I get the axe wedged in the wood (duh), but instead of going all the way through like that, I get out a hammer and use it on the axe (which applies a downward force), and thus the wood is split. (I may draw a picture if this is hard to understand)

    Now my question is this, it is torque because the hammer applies a downward force, which is perpindicular to the level arm (the axes handle). Thus, it is torque.

    Torque is [tex]\tau[/tex]=r x F right?

    Now, sometimes when i hit the axe w/ the hammer I hold the axe very close to where the hammer strikes (short lever arm), and other times I keep it far away (long lever arm).

    Now, by the torque equation I should feel more force when my hands are further away (and I believe this is true because it is much harder to hold onto the axe).

    However, my hands hurt more if I keep my hands closer to the area of impact. That is, my hands hurt more when there is a SHORT lever arm. I'm wondering why this is? If the force increases w/ the length of the level arm wouldn't my hands hurt more then?

    I'm probably just forgetting a factor, but I'm not sure. If I had to guess, I would say that it is because when the lever arm is longer I can't quite hold onto the axe. If I let go earlier I the time over which the force is felt would be less and thus I would feel less force with the longer lever arm. Basically, just human error. I'm just wondering if my guess is correct?

    EDIT: and I know that there are a ton of different reasons that this could possibly happen, I was just wondering if my guess is feasible? And maybe what other reasons there could be for it.
     
    Last edited: Jan 24, 2010
  2. jcsd
  3. Jan 24, 2010 #2
    I think the reason why your hand doesn't hurt as much when you are holding the axe far from the point of impact is because the shock of the hit gets dissipated along the length of the handle. However, when your hand is close, your hand absorbs most of the shock before it reaches the other end of the handle.
     
  4. Jan 24, 2010 #3
    Yeah I had thought of that, but dismissed it initially. Now that I think about it again though, that's probably it.

    I realized my problem. The torque is at the area of impact, and it gets bigger the further that point is from the CM. I forgot about the CM. I'm assuming my hand positioning affects the torque because I need to apply an upward force to keep the axe from being knocked out but that shouldn't make too much of a difference.

    SO yeah, you're probably right about it just being the force dissipating. I feel quite dumb for dismissing that before :\
     
  5. Jan 24, 2010 #4
    Are you using a felling ax for chopping wood? Like that of a Michigan or a Californian head? Or are you using a maul? You shouldn't have a problem splitting wood with a maul in one chop, but a felling ax would have that problem.

    Also, have you tried, instead of hitting the back of your ax with a hammer, lifting the piece up with the head and cheek still inside the wood and dropping it back down? It saves a lot of effort while chopping wood if you get a knotty piece.
     
  6. Jan 24, 2010 #5
    Oh no, I'm not having any problem chopping the wood, I was just wondering about the physics behind it =)

    and yeah, that's exactly what I do for the knotty pieces. It's pretty useful
     
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