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NEET 2007 (AIPMT) · Velocity, Acceleration & Variable Motion

Velocity, Acceleration & Variable Motion question from NEET 2007 (AIPMT)

Q40NEET 2007 · AIPMTMedium

Velocity, Acceleration & Variable Motion

The position x of a particle with respect to time t along x-axis is given by x = 9t2 −- t3 where x is in metres and t in seconds. What will be the position of this particle when it achieves maximum speed along the + x direction?

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Answer: (a)

  1. v=dxdt=18t−3t2v = \dfrac{dx}{dt} = 18t - 3t^2
  2. Speed is maximum when a=dvdt=18−6t=0⇒t=3 sa = \dfrac{dv}{dt} = 18 - 6t = 0 \Rightarrow t = 3\text{ s}
  3. x(3)=9(9)−27=54 mx(3) = 9(9) - 27 = 54\text{ m}
  4. So the answer is (a) 54 m.
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