posted by Hester .
A bridge is 40.0 m. A car weighs 1.5 x 10^4 N and it is parked with its center of gravity located 12.0 meters from the right pier. What upward support force must be provided by the left pier?
draw the figure. Put the weight of the bridge in the center, and the car as determined.
Sum moments about the right pier.
so, if you know the weight of the bridge, you have it. Surely you don't want to ignore that, however, your teacher is your teacher.