Question

The free-body diagram below represents the force of several vehicles driving across a bridge. Assume that the bridge is in static equilibrium and that it has zero weight, and solve for the unknown reaction force.

Answer 1

In order to calculate the unknown reaction force, we need to know that the sum of forces pointing down is equal the sum of the forces pointing up, so all forces will be in equilibrium.

So we have:

$\begin{gathered} 17800+150000+13200=121000+x \\ 181000=121000+x \\ x=181000-121000 \\ x=60000 \end{gathered}$