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ENGR5004 / Week 6
Dynamics L12 Worked example 1TutorialOld spec ENGR2162:28 min

ENGR216 Dynamics L12 worked example 1 (slides 11-13) official answers

Link AB (0.4 m) is pinned to the ground at A and to link BD (0.4 m) at B; D is pinned to a block that slides on a horizontal surface level with A. At the instant shown AB rises at 45∘45^\circ from A, BD falls at 45∘45^\circ to D (the angle ABD is 90∘90^\circ), and block D moves to the right at vD=3v_D = 3 m/s.

Find the angular velocities of links AB and BD.

Links AB and BD, each 0.4 m, at 45 degrees to the horizontal with a right angle at B; A is a ground pin, D is pinned to a block moving right at 3 m/s.
Links AB and BD, each 0.4 m, at 45 degrees to the horizontal with a right angle at B; A is a ground pin, D is pinned to a block moving right at 3 m/s.
Formulas you may need
  • Instantaneous centre of zero velocity: intersection of the normals to two known velocity directions; v=ω r/ICv = \omega\,r_{/IC} (learn this)
  • Fixed-axis rotation: vB=ωAB rB/Av_B = \omega_{AB}\,r_{B/A}, perpendicular to AB (learn this)