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ENGR5004 / Week 3
Dynamics L5 Worked example 1TutorialOld spec ENGR216Third6 min

ENGR216 Dynamics L5 worked example 1 (slides 10-12) official answers

Two planes fly in the same horizontal plane. Plane A flies due east (+x+x) at vA=650v_A = 650 km/h. Plane B flies at vB=800v_B = 800 km/h along a line inclined at 60∘60^\circ to the east-west line, heading towards the south-west (its velocity points down and to the left in plan, at 60∘60^\circ below the −x-x direction).

Find the velocity of plane B relative to plane A, vB/A\mathbf v_{B/A} (magnitude and direction).

Plan view: plane A flies to the right at 650 km/h; plane B flies at 800 km/h down and to the left along a line at 60 degrees to the horizontal.
Plan view: plane A flies to the right at 650 km/h; plane B flies at 800 km/h down and to the left along a line at 60 degrees to the horizontal.
Formulas you may need
  • Relative velocity (translating axes): vB=vA+vB/A\mathbf v_B = \mathbf v_A + \mathbf v_{B/A} (learn this)
  • Law of cosines c2=a2+b2−2abcos⁡Cc^2 = a^2 + b^2 - 2ab\cos C and law of sines asin⁡A=bsin⁡B\dfrac{a}{\sin A} = \dfrac{b}{\sin B} (learn this)