Question
Please help, I don't understand how to do this.
replace the loading system by an equivalent resultant force and specify where the resultant's line of action intersects the member measured from A. Assume F1 = 2501b, F2 = 70lb and F3 = 100lb. (Figure 1) Determine the magnitude of the resultant force. Express your answer to three significant figures and include the appropriate units. Determine the angle between the resultant force and the x axis. Express your answer using three significant figures. Determine where the resultant's line of action intersects the member measured from A Express your answer to three significant figures and include the appropriate units.
Explanation / Answer
F = (F2*sin30 + F3*(3/5))i + (F1 + F2*cos30 -F3*(4/5))j F = (70*sin30 + 100*(3/5))i + (250 + 70*cos30 -100*(4/5))j F = 95i + 230.62j |F| = 249.42 N {Part A} angle = arc tan(230.62/95) = 67.61 degree {Part B} Moment about A M = (F1*3 + F2*cos30*9 -F3*(4/5)*6 M = 815.6 = 230.62*d d = 3.54 ft from A {Part C}