2024 TWO(b)

Achievement
Question
An object is travelling in a straight line. Its displacement, in metres, is given by the formula

s(t)=ln(3t2+5t+2)s(t)=\ln(3t^2+5t+2), where t>0t>0 and tt is time, in seconds.

Find the velocity of this object when t=1t=1 second.

*You must use calculus and show any derivatives that you need to find when solving this problem.*
Official Answer
dsdt=v=6t+53t2+5t+2\dfrac{ds}{dt}=v=\dfrac{6t+5}{3t^2+5t+2}

t=1t=1 gives v=1110=1.1m sec1v=\dfrac{11}{10}=1.1\,\text{m sec}^{-1}

Units not required.
Grading Criteria

Achievement (u)

  • Correct derivative.
    AND
    Correct value for velocity of v=1110=1.1v=\dfrac{11}{10}=1.1.

Merit (r)

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Excellence T1

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Excellence T2

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Video Explanation
2024 NCEA L3 Calculus Exam Walkthrough by infinityplusone(starts at 20:50)
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