Getting magnitude and direction of 3 forces

[anthonyk2013]

I have completed this question but I am not sure I am right.

3 co-planer forces acting at a point 0, 100KN→ at 0deg from o point, 70KN→120deg from o point and 50KN →210deg from o point (hope that make sense, can't draw it).

using a scale of 10mm+10KN determine, By means of polygon of forces method magnitude and direction of their resultant.

force--------Fx=fcosθ------------Fy=sinθ
100KN----100cos0=100 ------100sin0=0
70KN------70cos120=-35 ---- 70sin120=61
50KN------50cos210=-43 ---- 50sin210=-25
-------------------Ʃfx=22 ------------Ʃfy=36

Resultant=42.19KN

Tan-1=o/A=36/22=58.57deg

 

[Doc Al]

Looks reasonable to me--except that the units are KN, not N. (You did it using components, but I suppose they wanted you to use a graphical method.)

 

[anthonyk2013]

Looks reasonable to me--except that the units are KN, not N. (You did it using components, but I suppose they wanted you to use a graphical method.)

When I draw it on graph paper I measured the resultant and it was very close to the one I worked out,
the angle on the other hand is off on the graph it 75deg.