Meriam, Kraige & Bolton — Internal Forces and Moments: Problem 7_18

⚡ Mecademy AIENG정역학 · ch7  Problem Statement In testing the design of the screw-lift jack shown, 12 turns of the handle are required to elevate the lifting pad 1 in. If a force applied normal to the crank is required to elevate a load , determine the efficiency of the screw in raising the load. Problem 7/18 (a) Determination of Mechanical Efficiency 1. Formula: Efficiency is defined as the ratio of useful output work to the total input work: Where: Output work Input work 2. Substitution: Substitute the given values into the expression: Load, Elevation, Applied force, Number of turns, Crank radius, 3. Calculation: Perform the intermediate operations: F=10 lb L=2700 lbe e= W in W out W = out L⋅Δh W = in F⋅s=F⋅(n⋅2πR) L=2700 lb Δh=1 in. F=10 lb n=12 R=6 in. e= 10 lb⋅12⋅(2π⋅6 in.) 2700 lb⋅1 in. W = out 2700⋅1=2700 lb⋅in. W = in 10⋅12⋅12π=1440π≈1440⋅3.14159=4523.89 lb⋅in. e= ≈ 4523.89 2700 0.59683 4. Result: ● Final Conclusion: The mechanical efficiency of the screw-lift jack in raising the load is approximately . This indicates that about of the input work is lost to friction within the screw mechanism. ✨ Final Answer Summary (a) Mecademy AI Solution · ENGProblem 7/18 e≈0.597 or 59.7% 59.7%40.3% e=59.7%