Meriam, Kraige & Bolton — Rigid Bodies: Equivalent Systems of Forces: Problem 3_76

⚡ Mecademy AIENG정역학 · ch3  Problem Statement During a test, the left engine of the twin-engine airplane is revved up and a 500-lb thrust is generated. The main wheels at B and C are braked in order to prevent motion. Determine the change (compared with the nominal values with both engines off) in the normal reaction forces at A, B, and C. Problem 3/76 (a) Change in the normal reaction force at wheel A ● Calculation Process 1. Present Final Formula: To find the change in the normal reaction at the nose wheel , we sum the moments about a transverse line passing through the main wheels and . where is the longitudinal distance from line to , is the generated thrust, and is the height of the thrust line above the ground. 2. Substitute Values: 3. Partial Operations: 4. Final Calculation: ● Final Conclusion: The normal reaction force at wheel increases by . (b) Change in the normal reaction force at wheel B ● Calculation Process AB C M = ∑ BC 0⇒d⋅ΔN − A T⋅h=0 d=12 ftBCAT=500 lb h=6 ft 12⋅ΔN − A 500⋅6=0 12ΔN = A 3000 ΔN = A = 12 3000 250 lb A250 lb 1. Present Final Formula: Since the thrust force vector is parallel to the longitudinal centerline (-axis), its moment about the centerline is zero. Therefore, the changes in the normal forces at the main wheels and must be equal to maintain lateral moment equilibrium. Using the vertical force equilibrium: 2. Substitute Values: Substitute and : 3. Partial Operations: 4. Final Calculation: ● Final Conclusion: The normal reaction force at w