At equilibrium when no motion or acceleration of the body is occurring, the torque of the resistance force equals the torque of the holding force: force times the force arm equals resistance times the resistance arm. F x a = W x b for each type of lever.
Brunnstrom, page 37
Torque = force times perpendicular distance
static equilibrium for torque = 0
static equilibrium for force = 0
My question: what the hell?!
Okay, I'm not THAT clueless. But I am having some difficulty knowing when to plug in certain numbers. My professor laid it out in an obvious fashion, but I didn't get it.
The forearm was the example. The elbow joint is the axis. The forearm is at 90 degrees flexion and paralell to the floor. The hand is holding a 10 pound weight. The perpendicular distance of the resistance arm is 12 inches (axis to weight), the perpendicular distance of the force arm (axis to muscle pull) is 2 inches. We do not know the force of the muscle is exerting (X), but we are looking for how much it has to exert to hold up the 10 lbs.
10 lbs x 12 in = 120 lbs in
2X = 120
X=60
I'm getting it, but I'm not.
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