- #1
Francis Hannah
- 7
- 0
For the structure, find the distance from O (in direction OA) to the point where the resultant force-couple system of the forces shown should have a resultant couple of zero. Give answer in metres.
a=90 N, b=289 N, c=549 N
Clockwise negative, anticlockwise positive.
Moment at a = (1+2+2.5cos45)(90) = 429.099 Nm
Moment at b = -(2.5sin45)(298) = -510.885 Nm
Moment at c = -(1)(459) = -549 Nm
Hence, the resultant moment = -630.7856 Nm
Forces in the x-direction = 289 N
Forces in the y-direction = -459 N
Resultant force = 542.404 N.
Hence m = fd, so d = m/f ⇒ d = -630.7856/542.404 = -1.163.
Absolute value of d = 1.163m
However, the answer I got is somehow incorrect, and I have no idea where I've gone wrong!
What does it mean by a "resultant couple of zero"?
Thanks for helping :)