Posted by: ray porco () on Tue May 25 03:24:09 2004

>>> jack, with your busy schedule and all, i think you overlooked a question i asked you recently...i'll repeat it:
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> upon reflection i think teacherman made a valid point...if a boxer delivers a blow to the opponent's face, is that torque?
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> i understand your point, which was that even though the bottom hand is "stationary" rather than actually moving in the opposite direction, this can result in two forces acting in opposition to each other...but is that torque?...if not, what do you call it?...standing on the ground creates two forces acting against each other, pushing your hand against the wall results in two forces acting in opposition, but i don't think any of us call that "torque".....
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> Hi grc
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> It can get confusing, can’t it? – Torque is a measure of turning power applied to an object that determines its rate of angular displacement. To induce rotation requires forces being applied to the object from opposing directions. Basically, the amount of torque applied depends on two key factors. (1) The vectored amount of the forces applied. (2) The length of the fulcrum arm between the two forces. Note: grc, you can apply much more torque to a nut with a longer wrench than a short one because of the fulcrum arm length.
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> In order to answer your questions regarding the ‘wall’, there is an important factor to keep in mind. – Regardless of the amount of forces applied, as the length of the fulcrum arm (distance between two forces) approaches zero, torque approaches zero. In other words, two directly opposing forces generate zero torque.
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> When you push your hand against the wall, the wall pushes directly back with the same force. Therefore, no torque was applied to the wall.
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> Jack Mankin
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>


Two key points that I think you should note:

1. Torque can be applied in only one direction to induce rotation. If you place a wrench on a nut, you can rotate the nut by applying force (in only one direction) to the handle of the wrench.

2. Torque can be applied in a direction other than 90 degrees to the lever arm. Torque can be computed this way adding sin/cosin.

ray porco