Vector calculus — Question 34
Original QCE Vault practice · 6 marks
Q34 · Practice questionComplex familiar6 marks
QUESTION 34 (6 marks)
A particle follows the path r(t)=(3cost,2sint),0≤t≤2π. 
a)Obtain a Cartesian equation of the path.
[2 marks] b)Determine the velocity and speed at t=π/2. [2 marks] c)Determine the acceleration at t=π/2 and explain its direction relative to the centre of the ellipse. [2 marks] WORKED SOLUTION
Practice marking scheme
6 marksANSWER(a) x2/9+y2/4=1; (b) (−3,0), speed 3; (c) (0,−2), towards the centre. Worked solution
(a) x/3=cost and y/2=sint, so 9x2+4y2=1. (b) v=(−3sint,2cost), so v(π/2)=(−3,0) and the speed is 3. (c) a=(−3cost,−2sint), so a(π/2)=(0,−2). At this time the particle is at (0,2); its acceleration points towards the centre (0,0). Obtains the Cartesian ellipse.
[2 marks]Determines velocity and speed.
[2 marks]Interprets its direction.
[1 mark]Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
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