Statics - It seems simple, but there must be a catch

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Femme_physics
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Statics - It seems simple, but there must be a catch...

(Sorry if I'm overasking for one day. Clearly I'm doing a marathon of statics exercises today and you're all super helpful ^^)

Homework Statement



This structure is made out of 2 weightless parts, BCD and AC, connected by joints. At C is acting a pair of forces, their moment is
m = 50 [Nm]

Calculate the support forces at A, B, and C

The measurements are in mm



The Attempt at a Solution


Attached. The answers for Rb, Ra, and Rc are 390.60 [N]

Not sure what I'm doing wrong..?
 
Attachments
  • Handwritten solution on grid paper: a bent frame with joints A, B, C, D and a moment arrow at D, then the equation sum of moments about A is zero giving Bx = 312.5 N, and beam BD with its free-body forces, giving By = 312.5 N and RB = 441.94 N.
    needhelp.jpg
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Last edited by a moderator:


Do you have a statics exam coming up or something?

You forgot the moment of Bx.
 


Not forgot, rather didn't know it exist! But, that's right --that tiny angle there counts for length! *smacks forehead* I'll redo it right now.

Do you have a statics exam coming up or something?

More like 3! Two internal and one big end-year external one coming up the following weeks, and months. Time for the one girl to prove her mettle against the boys club :D
Actually we were given a notebook with a questions and last semester I got some praises for finishing the entire notebook (which had A LOT of questions). I did get a lot of help from this forum, esp. tiny-tim. I was thinking to do the same with this notebook. We actually got a solution manual this semester, but I sometimes want to fully fathom the question and try other methods to solve it. I'm a mechanics explorer ^^

I'm a bit obsessed though, I admit, I've been now self-studying for 16 hours straight and got some coffee next to me as I'm insistent on not going to bed rather solve more problems...picturial proof attached lol! (and yes, in case you're wondering, I did spill that coffee 1 minute after the shot heh)

Thanks a lot for all your help Serena!
 
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  • A student in a dark top leans over a desk writing in a notebook, with a calculator, a glass of dark coffee, and scattered papers and a backpack on the floor around them.
    picpove.JPG
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Femme_physics said:
More like 3! Two internal and one big end-year external one coming up the following weeks, and months. Time for the one girl to prove her mettle against the boys club :D

So are you aiming for top-of-the-class? That'll show them!

Femme_physics said:
I'm a mechanics explorer ^^

That's great! :smile:
I hope to see some more exploring!

Femme_physics said:
I'm a bit obsessed though, I admit, I've been now self-studying for 16 hours straight and got some coffee next to me as I'm insistent on not going to bed rather solve more problems...picturial proof attached lol! (and yes, in case you're wondering, I did spill that coffee 1 minute after the shot heh)

Thanks a lot for all your help Serena!

LOL! And I appreciate you took the time to take the pic!
 


That's the least I can do :) You'll definitely be seeing more exploring, no worries there :D

Yes, I am aiming for the top of the class! What a hoot will it be if the best student in mechanical engineering is a gurl? :)