Two$-$Dimensional Description and the Moment Vector

Determine the moment of the $400-N$ force in Fig. $4\mathrm{.}13$ about $O.$

Strategy

We will determine the moment in two ways: $($a$)$ We can use the two$-$dimensional description of the moment. We will express the force in terms of its components and determine the moment of each component about $O$ by multiplying the magnitude of the component and the perpendicular distance from $O$ to its line of action. $($b$)$ We can obtain the vector description of the moment by using Eq$.(4\mathrm{.}2).$