【Daily Question】Theoretical Foundation 2020.01.15

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Multiple-choice question: The straight rod BC in the diagram is subjected to loads F and q; BC = L, and F = qL, where q is the load intensity with units of N/m, the concentrated force is expressed in N, and length is in meters. Then the resultant torque of this primary force system about point O is ( ). Answer: A. The moment of the resultant force is equal to the algebraic sum of the moments of the individual forces. The line of action of F passes through point O, resulting in a zero moment about O. The resultant force of the uniformly distributed load q is qL; its line of action passes through the midpoint of rod BC and is perpendicular to rod BC, passing through point O, so its moment about point O is also zero. Tip: An additional reward will be given to those who can explain the problem-solving process; the answers can be seen here!