(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Hi everyone, I've been stuck on this relatively very simple problem for quite a while now and even after solving I'm still getting two answers while the book only lists one.

Question: If block D weighs 300 lb and block B weighs 275 lb, determine the required weight of block C and the angle (theta) for equilibrium.

So I did the usual since it's in equilibrium then F_{x}= 0 and F_{y}= 0.

So, F_{c}(cos30) - 275(cos[itex]\theta[/itex]) = 0

and F_{y}(sin30) + 275(sin[itex]\theta[/itex]) - 300 = 0

Then after finding cos[itex]\theta[/itex] in terms of F_{c}and substituting, you get this equation: 158.7cos[itex]\theta[/itex] + 275sin[itex]\theta[/itex] = 300

The answer listed is: [itex]\theta[/itex] = 40.9 and F_{c}= 240lb

Can anyone please tell me how to solve the equation above? I tried using the trig identity (square of cos plus square of sin = 1) but I got two answers, one was similar to the book ([itex]\theta[/itex] = 40.9, and one was [itex]\theta[/itex] 79). Thing is, when I use the second value I got (79) in the equations above, it works for all.

I'd appreciate some clarification on this problem! Thanks.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Simple Force in Equilibrium

**Physics Forums | Science Articles, Homework Help, Discussion**