Engineering Board Exam Reviewer · Engineering Mechanics · hard
A particle is held in equilibrium by three coplanar forces. Force F1 = 54 N acts at 15° from the positive x-axis, and Force F2 = 68 N acts at 105° from the positive x-axis. What must be the magnitude of the third force, F3, for the particle to remain in equilibrium?
- 122
- 86.83
- 14
- 69.47
Answer
B. 86.83
Solution
For equilibrium, F3 must balance the resultant of F1 and F2. Fx = 52.16 + -17.6 = 34.56 N, Fy = 13.98 + 65.68 = 79.66 N. The magnitude of F3 = sqrt(ΣFx² + Fy2) = 86.83 N (acting opposite to this resultant).
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