A bridge, constructed of 11 beams of equal length L and negligible mass, supports an object of mass M (as http://masteringphysics.com/problemAsset/1010954/21/MFS_st_1_a.jpg).

Throughout this problem, use g for the magnitude of the acceleration due to gravity.

Question

A bridge, constructed of 11 beams of equal length L and negligible mass, supports an object of mass M (as http://masteringphysics.com/problemAsset/1010954/21/MFS_st_1_a.jpg).

Throughout this problem, use g for the magnitude of the acceleration due to gravity.

anonymous · Answer

Link didn't work... Here's the pic.

anonymous · Answer

Question is: Find F_P, the vertical force that pier P exerts on the left end of the bridge.

anonymous · Answer

Yes, $F_p$ and $F_q$ are the normal forces exerted on the truss by the pier.

anonymous · Answer

so are they both just mg? or mg/2?

anonymous · Answer

nevermind, it was 2/3 mg b/c of m's placement

anonymous · Answer

Indeed. You'll need to sum torques about either P or Q to determine the reaction forces at P and Q.

anonymous · Answer

Yes, Fp and Fq are the normal forces exerted and the tension

anonymous · Answer

Use (mv^2 + 2mv^2/3) /2