Thread: Question about resultant forces

Hi. I need a little help with dealing with Q6 parts (b) and (c) on page 67 on the following link: Mechanics: No. 1 - Google Book Search

If there are any troubles loading the page, I'll explain the question from here on.

"Forces P, Q, R and S act on a particle at O in the plane of the coordinate axes Ox, Oy, making angles p, q, r, s respectively with Ox, each angle being measured in the anticlockwise sense. By drawing a polygon of forces, fine the magnitude of their resultant and the angle it makes with Ox when:

(b) P = 3N, Q = 3N, R = 5N, S = 5N, p = 0 degrees, q = 40 degrees, r = 130 degrees, s = 220 degrees

(c) P = 1N, Q = 2N, R = 3N, S = 4N, p = 10 degrees, q = 70 degrees, r = 100 degrees, s = 300 degrees"

I have attempted to draw a polygon of forces in (b) and keep getting a resultant force of 5.64N whilst in (c), I've had no success in drawing the polygon. I would appreciate any help.

With "polygon of forces" method, it is necessary to draw graphically the forces end to end, so you need a protractor and a scale. I cannot show that here, so I cannot be of help.

Analytically, or by the usual summation of vertical, and horizontal, forces, those system can easily be solved for their resultants.