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ENGR5004 / Week 6
Dynamics L11 Worked example 2TutorialOld spec ENGR2162:28 min

ENGR216 Dynamics L11 worked example 2 (slides 14-15) official answers

Crank OA (length 0.3 m) rotates anticlockwise about the fixed pin O at 12 rad/s. At the instant shown OA is vertical with A above O. Rod AB (length 0.6 m) connects A to a piston B that slides in a vertical guide; B is level with O, to the right, and AB makes 30∘30^\circ with the horizontal.

Find the velocity of piston B and the angular velocity of rod AB.

Vertical crank OA (0.3 m) rotating anticlockwise at 12 rad/s; rod AB (0.6 m) at 30 degrees to the horizontal down to piston B in a vertical guide, level with O.
Vertical crank OA (0.3 m) rotating anticlockwise at 12 rad/s; rod AB (0.6 m) at 30 degrees to the horizontal down to piston B in a vertical guide, level with O.
Formulas you may need
  • Fixed-axis rotation: vA=ωOA×rA/O\mathbf v_A = \boldsymbol\omega_{OA} \times \mathbf r_{A/O} (learn this)
  • Relative velocity: vB=vA+ωAB×rB/A\mathbf v_B = \mathbf v_A + \boldsymbol\omega_{AB} \times \mathbf r_{B/A} (learn this)