Question

Four forces act on an object such that the object is at rest. Three of the forces are given by

F1 = 2i −2j, F2 = i −4j, F4 = −3i −5j. Determine F3 and its magnitude

Answer 1

Let $F3=ai+bj.$ Then

$$2i −2j+ i −4j+ai+bj −3i −5j=0i+0j$$ $$a=0, b=11$$ $$F3=11j$$

$$|F3|=11$$