[Daily Question] Theoretical Basis 2020.01.12

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Multiple choice questions: The structure is as shown in the figure. Point H of rod ED is pulled by a horizontal gate, and the pin C on it is placed in the smooth straight groove of rod AB. The weight of each rod is not counted. It is known that Fp=10kN. The angle between the line of action of the restraining force at pin C and the positive direction of the x-axis is ( ). A. 0° B. 90° C. 60° D. 150° Answer: D. Take rod AB as the research object and draw the force diagram of rod AB, as shown in the figure below. The pulling force T of pulley B in the figure is the same as Fp, and the magnitude is both Fp, so the direction of the constraint reaction force FB at point B is at an angle of 45° to the direction of Fp, as shown in the figure. Since the smooth straight groove of rod AB is in contact with the smooth surface of pin C, FC is perpendicular to the smooth surface and forms an angle of 150° with the positive direction of the x-axis.: Those who can explain the problem-solving process will be given extra rewards, and the answers will be visible in the replies!