Problem 8.4. Four equal rods, each having mass of 10 kg and length {16 m, are hinged together to form a rhombus (Fig. REA). The angle the rods make with the horizontal plane, 6, is 45 at the instant the system is let go from rest. Use the conservation of energy principle for the sys- tem of four links to determine the kinetic energy of the system when the angle 9 reduces to 30. Note that the kinetic energy of the system is the sum of kinetic energy of the four links. What is the work done by the reaction forces at B and C on the part of the system composed of the rod a and E1? Answer: T = 48.? N-m, W = 4.6 N-m. FIGURE P.8.4. A structure consist- A ing of four equal rods that are con- m nected to each other by hinges. m b B OC m C m D