Physics Help Forum Statics - Moments

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Mar 17th 2017, 04:22 PM #1 Junior Member   Join Date: Mar 2017 Posts: 1 Statics - Moments Doing a question where you have to determine the moment at a particular point.. So far I've only been able to find the j (y) and i (x) components for two forces... but I have no clue what to do now.. ps - I don't know if my working is even right! NEED HELP Attached Thumbnails
 Mar 18th 2017, 07:54 AM #2 Physics Team     Join Date: Jun 2010 Location: Naperville, IL USA Posts: 2,179 For each of the three applied forces you need to determine the x- and y-components of those forces, then multiply each by the x- or y-distance, respectively,from point A, then sum up the results. To get you started: the 15 kN force is purely vertical, and its x-distance from A is 4m, so it contributes -15x4 = -60 kN-m of torque. It has a negative sign because it acts in a clockwise direction relative to A. Now consider the 21 kN force: it has components in both the x- and y-direction, so first you need to compute them. Then you need to determine the x- and y- offsets from point A. The x-distance is 4m+4m+3mcos(40), and the y-distance is -4m tan(15) +3m sin(40). Do you see why that is? OK, now you take it from here, and be careful as to whether each component of torque is positive (counter clockwise relative to point A) or negative (clockwise). Post back with your results and we'll review it for you. Last edited by ChipB; Mar 19th 2017 at 02:11 PM.

 Tags moments, statics

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Sylar New Users 2 Dec 2nd 2016 06:17 AM electrogeek Equilibrium and Elasticity 6 Nov 8th 2016 07:58 AM vishak95 Kinematics and Dynamics 1 Mar 14th 2013 08:57 AM bradycat Kinematics and Dynamics 7 Jan 28th 2011 12:03 PM ManyArrows Kinematics and Dynamics 2 May 5th 2009 03:59 PM