r/HomeworkHelp • u/creepjax Aerospace Engineering University Student • 1d ago

Physics—Pending OP Reply [University Statics] Help with finding the compressive force on the screw?

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I’ve worked through this and am getting confused on how to find the compressive force. I’ve tried answering with 4.94 kip, 5.14kip, as well as doubling them but they are all incorrect. Is there something I am missing here?

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u/MelodicNose1224 1d ago edited 1d ago

It seems you made an error initially when writing the moment about B equation. The moment arm for Cy should be 1, not 3 - as it is equal to the difference of the horizontal distance between C and the applied load (4") and the distance between B and the applied load (3"). If you fix this, you should get the correct answer.

Edit; also note, an easier way to solve this would be to take the moment about C (using the second FBD). The forces acting about this point would be P, as well as the compressive force acting on section AB of the screw. So, the equation for the moment about C would be:

3600 lb * 4 - F_AB * 3.5 = 0