A uniform bridge span weighs 70.0 kN and is 40.0 m long.An automobile weighing 15.0 kN is parked with its center of gravity located 15.0 m from the right pier.What upward support force does the right pier provide?
A)40.6 kN
B)51.3 kN
C)25.6 kN
D)44.4 kN
E)42.5 kN

Question

Quizplus · Accepted Answer

The total weight of the bridge and the car is 85.0 kN. Taking moments about the left pier, the moment due to the bridge is (70.0 kN * 20.0 m) and the moment due to the car is (15.0 kN * 25.0 m). Setting the sum of moments equal to the moment due to the right pier's force (F_right * 40.0 m), we solve for F_right to find it is 44.4 kN.

A Uniform Bridge Span Weighs 70