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?

Question

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?

bobpursley · Answer

draw the figure. Put the weight of the bridge in the center, and the car as determined.

Sum moments about the right pier.
clockwise positive.

LeftPierforceup*40-weightbridge*20-weightcar*12=0

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.