7.4 How to replace 3D forces by a Force-Couple system at a specified point
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- čas přidán 28. 02. 2020
- This video tutorial explains how, a set of 3D forces acting on a rigid body, can be replaced by a Force-Couple system at a specified point.
More video on 3D Force-Couple system:
8.3 How to identify an equivalent Force - Couple system in 3D - • 8.3 How to identify an...
Good stuff, thank you
So if the force intersects with the x, y, or z axis there is no moment? I am talking about F3 at time 6:10 where there is no moment on the x axis because F3 is touching the x axis
Yes, you're absolutely correct - since F3 intersects x-axis it has no moment about this axis. As explained in the video, the force F3 has moment only about the z-axis.
why is there a moment in the z-axis for -120(0.1)k?
That is so because the 120 N force doesn't intersect the z-axis but its line of action is below the axis by a distance of 0.1 m. So it has a turning effect about that axis and the moment vector is in negative z direction. Hope that helps!
Also suggest you to watch another video - czcams.com/video/y4xJVPVyj_Q/video.html (Geometric approach to moment computation) and that would help in 3D visualization.
how the forces come with negative sign?
Hello Kim: Could you be more specific. If the forces point towards negative x, y and z axes, they are written with a negative sign. Not sure if that answers your question... so please elaborate your question.
my lord -thank u for excellent lecture --u r very very good --please give solved examples on internet --thank u my lord
sir please give booklet with solved examples on internet
Noted your suggestion...I'll have to work on it and that takes fair amount of time. Thanks for your feedback.
@@VectorInMotion thank u my lord --it will be useful effort--amarjit advocate delhi high court -india
Just curious to know how practicing law at Delhi HC is related to learning Mechanics.
Moment =r×F not F×r
That is correct -- You can find moment by vector method too i.e. M = r x F. In this video, I haven't used the vector method for moment calculation. As the external forces are parallel to the three axes, it is pretty easy to visualize the direction of the moment vector and so the solution becomes fairly simple.