Q8 · 2021 · Technology-activeSimple familiar1 markMark as seenQUESTION 8The displacement (in metres) of a particle is given by s(t)=−3cos(t)+2sin(t)s(t)=-3\cos(t)+2\sin(t)s(t)=−3cos(t)+2sin(t), where ttt is in seconds. The instantaneous velocity of the particle at time t=π2t=\dfrac\pi2t=2π seconds is(A)−3 m s−1-3\text{ m s}^{-1}−3 m s−1(B)−2 m s−1-2\text{ m s}^{-1}−2 m s−1(C)2 m s−12\text{ m s}^{-1}2 m s−1(D)3 m s−13\text{ m s}^{-1}3 m s−1ABCDCheck answerQuestion linkReveal worked solutionOriginal paperWORKED SOLUTIONAnswer D1 markANSWERDWorked solutionv(t)=s′(t)=3sint+2costv(t)=s'(t)=3\sin t+2\cos tv(t)=s′(t)=3sint+2cost, so v(π/2)=3v(\pi/2)=3v(π/2)=3.Selects option D.[1 mark]Worked explanation by QCE Vault; correct option verified against the QCAA answer key.View the full QCAA marking guide