Physics center of gravity
posted by Kayla .
a uniform bridge span weighs 50000N and is 40m long. An automobile weighing 15000N is parked with its center of gravity located 12m from the right pier. What upward support does the left pier provide?

To get the upward force F on the left pier, set the total moment about the right pier equal to zero. The 50,000 N weight of the bridge acts through its CG, which is at the middle of the bridge. The weight of the car acts 28 m from the left pier,in the same direction. The force on the left pier produces a moment in the opposite direction.
50,000*20 + 15,000*28  F*40 = 0
Solve for F 
29500