Register to reply 
Statics: Find resultant force and couple moment 
Share this thread: 
#1
Mar913, 06:02 PM

P: 165

Calculate the resultant force’s magnitude and the couple moment. Let a = 3.70 m w1=5.35kN/m w2=4.00kN/m The resultant force of the triangle is 1/2(3.70)(5.35)=9.898 kN The resultant force of the rectangle is (4)(3.70) = 14.8kN So FR (The force's magnitude) is 24.69kN I found the location of the triangle's load to be 1/3(3.7) = 1.233m I found the location of the rectangles load to be 1/2(3.70)+3.7 = 5.550m So I calculated the couple moment MRa (Taking counter clockwise to be POSITIVE) I get (9.898)(1.233)+(14.8)(5.55) = 94.3kN*m but when I put these answers down for MasteringEngineering, they are incorrect. Where did I go wrong? 


#2
Mar913, 06:36 PM

Homework
Sci Advisor
HW Helper
Thanks
P: 9,863

W1 and W2 are acting in opposite directions.
Even if you correct that your FR calculation will still be wrong. You don't want the total vertical force. You only want the load at A. To get that, take moments about B. When you take moments about A for the second part, W1 has a negative moment. (I assume it's only asking for the moment about A due to W1 and W2. If the joint at B is holding the beam then there will also be a moment from that, and the total moment will be zero.) 


#3
Mar913, 06:36 PM

Homework
Sci Advisor
HW Helper
Thanks
P: 9,863

W1 and W2 are acting in opposite directions.
Even if you correct that your FR calculation will still be wrong. You don't want the total vertical force. You only want the load at A. To get that, take moments about B. When you take moments about A for the second part, W1 has a negative moment. (I assume it's only asking for the moment about A due to W1 and W2. If the joint at B is holding the beam then there will also be a moment from that, and the total moment will be zero.) 


Register to reply 
Related Discussions  
Statics Question: Finding Resultant Moment  Engineering, Comp Sci, & Technology Homework  1  
Finding the resultant couple moment  Introductory Physics Homework  1  
Statics  Balancing moment and resultant force  Introductory Physics Homework  1  
Find the Moment (Torque) of the resultant in 3D (Statics)  Engineering, Comp Sci, & Technology Homework  5  
How to get mag. & angles of resultant couple moment  Introductory Physics Homework  1 