Shit is really pissing me off. Down to my last guess. Really thought I had it but apparently not cause MasteringEngineering sucks...

The chandelier is suspended from the wall and ceiling using rods AB and BC, which have diameters of 3 mm and 4 mm, respectively.

If the average normal stress in both rods is not allowed to exceed 140MPa , determine the largest mass of the chandelier that can be supported if θ = 45∘



I got the mass to be 535.8 kg. With rod BC being the limiting one.

e/ work that I've done:

140*10^6 = Force(AB)/pi(0.003)^2

140*10^6 = Force(BC)/pi(0.004)^2

And I'm pretty sure you have to set up a system of the sums of X and Y equaling 0. Then using substitution to solve for both Forces in terms of P.

Then plug that into the equation above, and whichever comes out smaller (after dividing the weight by 9.81 to get mass) is the answer.

This post was edited by MachoMonkey89 on Sep 22 2013 08:42pm

yes, what you said works, it's pick and choose



cos(30)(F_a) - (sqrt(2)/2)(F_c)=0 ----------x
sin(30)(F_a) + (sqrt(2)/2)(F_c)= weight of light ----------y

pick either case, it'd be smart to pick the smaller diameter
140*10^6 = Force(AB)/[pi(0.003)^2], 3958N

140*10^6 = Force(BC)/[pi(0.004)^2]. 7037N

, I'd decompose the force vectors into their x and y components , then just simply compare to see which one is going to exceed it first
so,
x=cos(30)3958= 1979
y=srt(3)/2 *3958 = 3427

4976 for x,y for 4mm
since 4976> all of the 3mm, then use the 3mm numbers
once you figure that out, you just plug in to get total y component


*note that it says mass too, so divide your force by 32.3m/s^2
answer should be around 168

This post was edited by saber_x3 on Sep 22 2013 11:05pm