November 11th, 2011, 01:06 AM  #1 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  can check this Q in moment
Hi  answer number 10 ) clockwise () antcolc wise (+) Moment of A 30(0) + 15 (4) + 25 (2) Ma = 170 Nm Moment of B = 30(2) + 15(0) + 25(2) Ma = 110 Moment of c = 30(2)  15(4)  25(0) Mc = 120 Nm  
November 11th, 2011, 11:35 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 20,746 Thanks: 2133 
You have the right method, but are making careless errors. Also, write "moment about A" instead of "moment of A". The diagram for problem 10 doesn't show the exact angle for the 15N force, so I'll assume that it is 45°. 10. Moment about A = 30(2)Nm + 15(2?2)Nm + 25(2)Nm = (110 + 30?2)Nm, which you can approximate if you like. Moment about B = 30(2)Nm + 15(0)Nm + 25(2)Nm = 10Nm exactly. Moment about C = 30(2)Nm + 15(2?2)Nm + 25(2)Nm = (110 + 30?2)Nm, which you can approximate if you like. Do you understand why the signs I've used are correct? 
November 11th, 2011, 11:45 AM  #3 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: can check this Q in moment
Hi , why you are divide by root of 2 15(2?2)Nm? and if the distance for example 4 it should be 15([color=#FF0000]4[/color]?2)Nm Note : m= Fx r r = perpendicular distance between the point or axis about which the moment is required and the line of action of the force ,,, thanks again. 
November 11th, 2011, 11:56 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 20,746 Thanks: 2133 
I didn't divide. I multiplied by sec(45°), which is ?2.

November 11th, 2011, 11:58 AM  #5 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: can check this Q in moment
Note : m= Fx r r = perpendicular distance between the point or axis about which the moment is required and the line of action of the force the 15X 2 not 15X 2?2) Is there angle ... ? ?? 
November 11th, 2011, 12:06 PM  #6 
Global Moderator Joined: Dec 2006 Posts: 20,746 Thanks: 2133 
I don't understand what you are asking. The 15N force is shown at an angle not specified very clearly. I assumed that the angle is 45°, so that the line of action passes through B and the perpendicular direction is the same as the direction of CA.

November 11th, 2011, 12:12 PM  #7 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: can check this Q in moment
Ac = root(4^2 + 4^2) = 5.6 Ac = 5.6 then for moment of A of 15 15(2.8 )Nm Is correct ? 
November 11th, 2011, 12:22 PM  #8 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: can check this Q in moment 
November 11th, 2011, 12:41 PM  #9 
Global Moderator Joined: Dec 2006 Posts: 20,746 Thanks: 2133 
How many significant figures are you supposed to use in approximate values? I suggest you redo problem 11, taking more care over signs and remembering to give the moment about D. 
November 11th, 2011, 01:05 PM  #10 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: can check this Q in moment
Number 11 ) moment of A the force 25 Negative ()


Tags 
check, moment 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Second moment finite then first moment finite  blabla  Advanced Statistics  6  July 12th, 2014 01:08 PM 
Calculation of the second moment  bvh  Advanced Statistics  1  March 6th, 2013 12:33 PM 
calculate the pth moment  bvh  Advanced Statistics  3  March 1st, 2013 12:27 PM 
[Help] Moment of Inertia!  s.nataniel1  Calculus  0  December 18th, 2011 04:52 AM 
nth moment  sangfroid  Advanced Statistics  1  March 3rd, 2008 07:10 AM 