If F_1 = 600N and Φ=30°, determine the magnitude of the resultant force acting on the eyebolt and its direction measured clockwise from the positive x axis.
Solution:
We will first draw the vector components out as follows.
Using our vector component diagram, we can start writing down the x and y components of each force (these x and y components are depicted in the dashed lines with the corresponding color to the force). Also note, we set F_1 to 600N and Φ to 30° as stated in the question.
(F_1)_x=600\text{ cos 30}^0=519.62\,N
(F_1)_y=600\text{ sin 30}^0=300\,N
(F_2)_x=500\text{ cos 60}^0=250\,N
(F_2)_y=500\text{ sin 60}^0=433.01\,N
(F_3)_x=450(\frac{3}{5})=270\,N
(F_3)_y=450(\frac{4}{5})=360\,N
To find the resultant, we will sum the x and y forces. To do this, we add the x components together, and we add the y components together, and in this case, we chose up and to the right as the positive side.
+\rightarrow\sum(F_R)_x=\sum(F_x)
(F_R)_x=519.62+250-270=499.62\,N
+\uparrow\sum(F_R)_y=\sum(F_y)
(F_R)_y=300-433.01-360=-493.01\,N
Notice we got a negative value for (F_R)_y. This simply means that the value is opposite to that of which we chose to be positive. In other words, the force is actually acting down. Thus, we can say:
(F_R)_y=493.01\,N\downarrow
We can now figure out the magnitude of the resultant force, F_R, using the Pythagorean theorem.
F_R=\sqrt{(F_R)_x^2+(F_R)_y^2}
F_R=\sqrt{(499.62)^2+(493.01)^2}
F_R=701.91\,N
good