How about another moment formula?

∑Mb = 1.0(Fa cosθ - Na sinθ) - 0.25 mg cosθ

(better check I have that oriented correctly)

Then you have three equations and three unknowns:

∑Fx = Fa - Nb sinθ + Fb cosθ

∑Fy = Na - mg + Fb sinθ + Nb cosθ

∑Mb = 1.0(Fa cosθ - Na sinθ) - 0.25 mg cosθ

(known: Nb=141.1, mg=24 x 9.81, sinθ=0.6, cosθ=0.8)

]]>I have had a brief look at the first problem, and understand it enough to know that I need to sit down quietly with a pad and paper to solve it. Can it wait a day?

]]>mechanics, or just can flick an eye on my calculations for this problem.

MathIsFun and mathysperson I'm sure will recognize one of these two problems.

http://engman.bravehost.com/mechanics/2probs.JPG

On 7.14 you can have a look of how far I've got, but I'm stuck.

http://engman.bravehost.com/mechanics/incomplete_solution714.JPG

7.39 I haven't a clue how to do it. The answer is: angle between 32.8 and 45 degrees. The 45 degrees

seems logic, and I guess that should calculate the intuition way. I'll buy that.

IF this is the wrong forum, if you wanna strictly do math around here, I would really appreciate a similar

forum with mechanics.

/Mr. G

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