Determine the reaction forces at the joints and the external torque applied to input link 2 of the four-bar linkage in the posture shown. For the constant angular velocity ω2 = 180kˆ rad/s, the known kinematics are α3 = 4 950kˆ rad/s2, α4 =

−8 900kˆ rad/s2, AG3 = 6 320ˆi + 750ˆj ft/s2, and AG4 = 2 280ˆi + 750ˆj ft/s2. The weights and mass moments of inertia of the links are w3 = 0.708 lb, w4 = 0.780 lb, IG2 = 0.025 8 in · lb · s2, IG3 =

0.015 4 in · lb ·s2, and IG4 = 0.011 2 in · lb ·s2.

∗ Unless instructed otherwise, solve all problems without friction and without gravitational loads.

Figure P12.3 RAO2 = 3 in, RO4O2 = 7 in, RBA = 8 in, RBO4 = 6 in, RG3A = 4 in, and RG4O4 = 3 in.