(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

http://imgur.com/BqIoe

There is a 50 meter bridge with two supports. The bridge has a mass of 80000kg. A truck of 30000 kg is 15m from one of the supports. What are the forces acting on the ends of the bridge?

Answers in back are F_a(support closer to truck): 598000 N and F_b: 480000 N

2. Relevant equations

torque = Force_perpendicular * distance

center of mass for uniform object is center of geometry

3. The attempt at a solution

Sum of Forces in y direction on bridge: = -80000g - 30000g + F_{n}A + F_{n}B = 0

Torque @ A = -15(30000) - 25(80000) + 50*F_{n}B = 0

F_{n}B = 490000

Torque @ A = 35(30000) + 25(80000) - 50*F_{n}A = 0

F_{n}A = 305000

What am I doing wrong? Any help is appreciated.

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# Homework Help: Basic torque question.

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