Im trying to solve this question. My question is: should i relocate vector (5N)
from third quadrant to first quadrant?
Because it is given with its head touching the axis, if i keep it in third quadrant its components (x and y) are going to be both negative. And if i relocate it to first quadrant, components are going to be positive, which changes the final answer.
Thank you in advance.
Yes, vectors representing forces are assumed, for being added, to have a common origin: you should relocate it in the first quadrant with its origin in 0.
The result is therefore:
$$\begin{cases}x&=&4&+&5 \cos 70° &+&1.5 \cos 120°\\ y&=&0&+&5 \sin 70°&+&1.5 \sin 120° \end{cases}$$