Physics Help Forum moment for 3D model

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Oct 30th 2015, 02:26 AM #1 Senior Member   Join Date: Jun 2014 Posts: 306 moment for 3D model in this case( involve 3D model) , it give the moment about the x , y , x' and y' axis .... can we find the moment about a specific point? (i.e. can we find the moment about the O ( centroid) ) ? Attached Thumbnails
Oct 30th 2015, 12:59 PM   #2
Physics Team

Join Date: Jun 2010
Location: Morristown, NJ USA
Posts: 2,344
 Originally Posted by ling233 . can we find the moment about the O ( centroid) ?
Sure. But it won't do you much good with respect to solving this problem though. Choosing to calculate moments through the x'- and y'-axes simplifies the problem nicely.

Oct 30th 2015, 07:59 PM   #3
Senior Member

Join Date: Jun 2014
Posts: 306
 Originally Posted by ChipB Sure. But it won't do you much good with respect to solving this problem though. Choosing to calculate moments through the x'- and y'-axes simplifies the problem nicely.
do u mean if i choose to find the moment about O , then i would have to find the moment about x , y , z axis about O ? in 3D question , if i choose to find the moment about a single point , then i would have to get the moment about the x, y, z of forces for the specific point ?

 Oct 31st 2015, 07:27 AM #4 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,344 You may choose to calculate moments about any point that you want. You have a total of 6 equations to play with at any point (three for forces in x-, y-, and z-dimensions and three for moments about x-, y- and z-axes). So as long as there are no more than 6 unknowns you should be able to find a solution (if one exists) no matter which point you choose to use as O, and no matter which particular directions you choose for x-, y- and z-axes (as long as they are independent, or better yet orthogonal to each other). However, by using some judgment about selecting which point to use and which way the axes are oriented you can often reduce these 6 equations to a more manageable number, thus making the problem much easier to solve. For example in this problem by selecting axes x', y' and z' the 6 equations simplify to become just two.

 Tags model, moment

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post mss90 Energy and Work 10 Dec 18th 2014 01:54 PM Jerromyjon Quantum Physics 5 Nov 22nd 2014 07:07 AM suvadip Light and Optics 1 Sep 10th 2013 09:38 AM Nimmy Advanced Electricity and Magnetism 0 Oct 27th 2011 10:00 AM soumyadip_2k Thermodynamics and Fluid Mechanics 1 Oct 5th 2008 07:44 AM