Calculating Force at Left Point of Support on Bridge

AI Thread Summary
To calculate the force at the left point of support on a bridge, it's essential to apply both the sum of forces and the sum of torques principles. The bridge, measuring 60 m and weighing 51,800 kg, supports a truck of 45,000 kg positioned 26 m from the left end. Identifying all forces acting on the bridge is crucial, as is selecting an appropriate pivot point for torque calculations. The discussion emphasizes the importance of correctly determining the axis for torque to arrive at the right answer. Proper analysis of forces and torques will yield the necessary calculations for the left support force.
kitty9035
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Homework Statement


A bridge of length 60 m and mass 51800 kg is supported at each end. A truck of mass 45000 kg is located 26 m from the left end.


Homework Equations


What is the force on the bridge at the left point of support?


The Attempt at a Solution



I know your supposed to use the sum of the forces equals zero. Then the sum of the torques equal zero, but i can't get the right answer!:eek:
 
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the reason is because you are trying to set the sum of all forces equal to zero when you don't even know enough forces. Look at torques. Try my suggestion on the other problem.
 
kitty9035 said:
I know your supposed to use the sum of the forces equals zero. Then the sum of the torques equal zero, but i can't get the right answer!:eek:
First identify all the forces acting on the bridge. Then show us exactly how you calculated the torques. (What point did you use as your pivot point?)
 
Its all about the choice of axis. You have all you need if you choose the right point
 

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