Moments - How are they actually calculated?

[012anonymousx]

Moments -- How are they actually calculated?

Hello, I have a question.

Is the moment calculated:

Force times the distance or

Force's perpendicular component (to axis) times the distance.

For example, let's say I have a stick.

Pulling on it is not moment.

So if I push at the stick to an angle, the way I calculate the force that the other side is applying is by taking the perpendicular component of my Fa and multiplying it by the distance.

Is that correct?

 

[rock.freak667]

Yes, when you are calculating moments, you would use the perpendicular component. The parallel component will not produce any moment as the perpendicular distance is zero.

 

[jhae2.718]

Mathematically, a moment is $\vec{l} = \vec{r} \times \vec{f}$. The magnitude comes out as $l = rf\sin\theta$, where $\theta$ is the angle between the position vector and the force vector. This is equivalent to saying that it is the perpendicular component of the force.

 

[012anonymousx]

Thank you!