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Solve rotational equilibrium problems using torque equations without forces involved. Calculate the weights and angles to determine the rotation center. Utilize trigonometry to find alpha and beam alignment.
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CH12.Problems JH.131
Take the lower center as rotation center then: • M2 (L/4) = M3 (3L/4) M2= 3 M3 • Now the upper center: • M1 (L/4) = (M2+M3) (3 L/4) • M1 = 3(M2+M3) = 3* 4 = 12kg • Only Torques, no forces!
-Ta + Tc cos30 = 0 Tc Sin30 -240 = 0 Only forces no torques
Project! Mg (L/2 sin alpha) is cw torque 2Mg (L) Sin(90-alpha) is CCW torque Then 2 Cos(alpha) = Sin(alpha) /2 Or Tan (alpha) = 4 alpha = 76 deg