The answer is that the resultant force is the vector sum of the component forces. In your simple example, where the component forces (F1 and F2) are at right angles to one another, as illustrated below, then the resultant force (r) is given by:
[tex]r= \sqrt{(f_{1}) {}^{2} +( f_{2})^{2} + 2f_{1}f_{2}. cos \: Θ, } \\ where \\ \: Θ, = angle \: between \: f_{1} \: and \: f_{2} \\ r = \sqrt{(2) {}^{2} + (5) {}^{2} + 2 \times 2 \times 5 \times cos90 } \\ \sqrt{4 + 25} = \sqrt{29} = 5.385 \\ nearest \: hundred = 5.39[/tex]
