PROBLEM 2.17 Solve Problem 2.4 by trigonometry. PROBLEM 2.4 Two structural members B and C are bolted to bracket A. Knowing that both members are in tension and that P = 6 kips and Q = 4 kips, determine graphically the magnitude and direction of the resultant force exerted on the bracket using (a) the parallelogram law, (b) the triangle rule.
SOLUTION Using the force triangle and the laws of cosines and sines: We have:
Then
γ = 180° − (50° + 25°) = 105°
R 2 = (4 kips) 2 + (6 kips) 2 − 2(4 kips)(6 kips) cos105° = 64.423 kips 2 R = 8.0264 kips
And
4 kips
=
8.0264 kips
sin(25° + α ) sin105° sin(25° + α ) = 0.48137 25° + α = 28.775° α = 3.775° R = 8.03 kips
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3.8° W