Meriam, Kraige & Bolton — Statics of Particles: Problem 2_51

⚡ Mecademy AIENG정역학 · ch2  Problem Statement 2/51 Compute the combined moment of the two 90-lb forces about (a) point O and (b) point A. Problem 2/51 (a) Moment about point ● Calculation Process 1. Present Final Formula: The combined moment about point is the sum of the moments of each individual force about that point. Using the standard convention where counterclockwise (CCW) is positive and clockwise (CW) is negative: where are the horizontal distances from the origin to the lines of action of the forces. 2. Substitute Values: From the diagram, point is the origin . - The first force acts upward ( direction) at a distance of to the left of . So, and . - The second force acts downward ( direction) at a distance of to the right of . So, and . 3. Partial Operations: 4. Final Calculation: ● Final Conclusion: The combined moment about point is in the clockwise direction. O M O O M = O ( r F − ∑ xy r F )= yx x F + 11y xF 22y x ,x 12 O O(0,0) F = 1 90 lb+y8+ ′′ 4= ′′ 12 ′′ Ox = 1 −12 inF = 1y 90 lbF = 2 90 lb −y4 ′′ Ox = 2 4 in F = 2y −90 lb M = O (−12 in)(90 lb)+(4 in)(−90 lb) M = 1/O −1080 lb⋅in (CW) M = 2/O −360 lb⋅in (CW) M = O −1080−360=−1440 lb⋅in O1440 lb⋅in (CW) (b) Moment about point ● Calculation Process 1. Present Final Formula: Similarly, the moment about point is calculated by summing the moments of each force about : where are the horizontal distances from point to the forces. 2. Substitute Values: Point is located to the left of . - Distance from to the upward for