Moments - How are they actually calculated?

  • #1

Main Question or Discussion Point

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, lets 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?
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
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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.
 
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  • #3
jhae2.718
Gold Member
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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.
 
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  • #4
Thank you!
 

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