Same-direction power-law catch-up

Same-direction power-law catch-up

Secondary 4
7 marks
Original parallel to supplied A Math Kinematics references

Particles \(P\) and \(Q\) move in the same direction along a straight line. At time \(t=0\), \(P\) is at \(O\) and \(Q\) is \(54\) metres ahead. Their velocities are \(6\sqrt{t}\text{ m s}^{-1}\) and \(3\sqrt{t}\text{ m s}^{-1}\), respectively.

  1. Find the positions of \(P\) and \(Q\), measured from \(O\), at time \(t\).[2]
  2. Hence determine the time at which \(P\) catches \(Q\).[3]
  3. Find the distance travelled by \(P\) by the catch time.[2]

Solution:

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Answer:(i) \(x_P=4t^{3/2}\), \(x_Q=54+2t^{3/2}\); (ii) \(t=9\text{ s}\); (iii) \(108\text{ m}\)

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