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Mechanical Engineering QUESTION #2476
Question 1
For a planar mechanism (\(f=3\)), the Grübler equation gives the mobility as \(M = 3n - 2c_5 - c_4\). A four-bar linkage has \(n=3\) movable links and \(c_5=4\) full revolute pairs. Its mobility is:
  • \(M = 0\) (structure)
  • \(M = 2\) (two-DOF mechanism)
  • \(M = 1\) (one-DOF mechanism)✔️
  • \(M = -1\) (overconstrained)
Correct Answer Explanation
For the four-bar linkage: \(M=3(3)-2(4)-0=9-8=1\). One DOF means one driver link is needed to fully define all positions.