Talk:Moment (physics)
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I came here from Wikipedia:Pages needing attention, and clearly this one fit the bill. It basically consisted of two separate, independent articles that shared little relation to one another. I've attempted to clean it up, but I think it still needs some more work, particularly because I simply copied the parallel axis theorem more or less verbatim from the preexisting article. Some fact checking would be great.
Also, the previous article listed a few examples about physical moments, but I think this rather belongs in the Physics Study Guide. I've moved the examples to this talk page. --Diberri | Talk 06:02, Jul 14, 2004 (UTC)
Examples
Examples:
A force of 85 N is applied to the lever arm shown above left. The length of the moment arm is 0.5 m. The moment of force at the joint to the arm can be calculated as:
M = F x d = 85 x 0.6 = 51 Nm (clockwise)
This moment can then be applied at any point along the arm. For instance, if the object being moved was located 0.2 m from the pivot point, known as the fulcrum, the amount of force applied would be 51 Nm / 0.2 m = 255 N, considerably more force than was put into the arm. For this reason a suitable arm and pivot point can allow human muscle to move objects that would otherwise be immobile. This is the principle behind the crowbar (or a nutcracker), for instance, where the blade operates applies the entire force being applied at the far end of the bar. With a common 1 m bar with a blade of perhaps 5 cm (0.05 m) long, the crowbar multiplies the force by 1/0.05 = 20 times.
Distinguishing terminology, difference from torque?
Correct me if I'm wrong.
- The moment which is the main subject of this article is often called the moment of force to distinguish it from other moments used in physics, such as the moment of inertia, as well as from the more general moment (mathematics).
- This moment of force is the very same thing as torque
- The statement in this article that torque "is a force" is poorly worded at best.
- The proper symbol for newton-meters is "N·m" or "N m" — not "Nm".
I also have some nagging doubts about the relative priority of the mathematics meaning and this physics meaning, but that's all they are is doubts—it would be nice to have some backup for the claim that the physics usage came first. Gene Nygaard 14:44, 27 Jan 2005 (UTC)