Science Q: Arm Wrestling "Friction"?

calcbandit · #1 08-22-2007, 11:29 PM

k, so I am involved in an arm wrestling competition. We lock fists and go at it.

We reach an entirely dead stand still (beat: I was arm wrestling a girl). I am trying my absolute hardest, and so is she, and we reach a stand still. There is a very little amount of back and forth action (maybe up to 5 degrees). After maybe 2 minutes of this, yes I am trying my hardest, the girl gives up.

We then went lefty, with the same result, although this time after 2 minutes I just declared "[censored] it, it's a tie."

So, the science question: how is this possible?

If my arm outputs 100.00 Newton's of force (I made this up), how is it possible that her arm just happens to be capable of the exact same force? If there was any difference in the forces, at any time in the 2 minutes, one of us would have won.

Clearly, to me, there is some "friction" in the system. What is your best guess as to how much force she would have to output to either win or lose against my 100.00N arm strength? 90? 99? How close are we in strength here?

And finally, where does this friction come from? What is it?

Sephus · #2 08-22-2007, 11:39 PM

[ QUOTE ]
how is it possible that her arm just happens to be capable of the exact same force?

[/ QUOTE ]

she isn't necessarily. there are a lot of possible explanations.

maybe when one of you starts to "win" a little, the other suddenly has an advantage, allowing him to take back the lead...

Lestat · #3 08-22-2007, 11:46 PM

<font color="blue">If there was any difference in the forces, at any time in the 2 minutes, one of us would have won.
</font>

I think your error lies here. I don't think it's true. The force is constantly changing. Maybe you're putting out 100.7 of Newton's force for a split seccond, only to drop back down to 100.05, while she ups it to 100.10 for the next 10th of a second, and so on.

Metric · #4 08-23-2007, 02:06 AM

My guess is that your strength is a function of position. Strongest when your arm is back a bit, and slightly weaker when it is far forward. So unless you are stronger over your whole range than she is, you'll naturally find an equilibrium point and sit there until one person gets fatigued.

SNOWBALL · #5 08-23-2007, 03:44 AM

maybe in arm wrestling, defensive positions have an advantage, which is to say that to move the person past 5 degrees, you need to exert 10% more force than they do for them to stop you.
Just a guess.

Cueballmania · #6 08-23-2007, 03:59 AM

I believe the answer is that we tend to reduce force to an equilibrium. Think about pushing a large box across carpet. A constant force should keep the box accelerating. I know when I push a box, the force decreases after I get it started and it reaches a steady speed. My force has reduced to equal the force of friction just as your force has reduced to equal the force of her arm.

Friction is not the driving force, this is a two forces problem. I'd hope that the torque in your arm can overcome air resistance.

joes28 · #7 08-23-2007, 05:53 AM

wow you cant beat a girl at arm wrestling? huge beat. I would have told her that I wasnt trying if I were you.

Kingdeuceoff · #8 08-25-2007, 01:59 AM

youre a pussy,eat some spinach

Duke · #9 08-25-2007, 02:42 AM

Let me hazard a guess: neither of you were holding on to the table with the other hand to get leverage.

If that is true, then let me also guess that you're of similar masses.

If that is true, then you should now be able to figure out why you locked up, even if one of you is a lot stronger.

The first guess is that a lot of people consider that cheating, and don't understand why arm wrestling competitions happen on tables with a nice grip to hold on to with your other hand.

If I'm wrong about that, then yeah the varying pressures that you were both applying were evening out, despite varying widely. It's also easy to kinda lock your muscles into a position and feel like you're trying to win, but if her hand disappeared yours wouldn't move.

PairTheBoard · #10 08-25-2007, 12:01 PM

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It's also easy to kinda lock your muscles into a position and feel like you're trying to win, but if her hand disappeared yours wouldn't move.

[/ QUOTE ]

This looks like an interesting phenomenon. So it's a psychological thing where you both sort of silently agree on maintaining the vertical position?

PairTheBoard