【Daily Question】Theoretical Foundation 2020.01.19

Thread Content

This post was last edited by Qingse Nianhua on 2020-1-21 at 18:02. Multiple-choice question: Forces F1, F2, F3, and F4 act on points A, B, C, and D in the same plane of a rigid body; the starting points of these force vectors are connected to form a rectangle, as shown in the figure. The simplified result of this force system is ( ). A. Equilibrium B. A resultant force C. A resultant couple D. A force and a couple Answer: C. Forces F1 and F4 remain unchanged; forces F2 and F3 are translated to point A, resulting in a planar system of concurrent forces and a planar system of couples, as shown in the figure on the right. The resultant vector of this planar force system is zero, but the moment of this planar couple system is not zero; therefore, the simplified form of this force system is a single couple. Tip: An additional reward will be given to those who can explain the problem-solving process; the answers can be seen there!