A force (10i + 4j)N acts on a body of mass 2kg which is at rest. Find the velocity after 3 seconds.

  • A \((\frac{5i}{3} + \frac{2j}{3})ms^{-1}\)
  • B \((\frac{10i}{3} + \frac{4j}{3})ms^{-1}\)
  • C \((5i + 2j)ms^{-1}\)
  • D \((15i + 6j)ms^{-1}\)
waec 2017furthermathematics

The correct answer is D. \((15i + 6j)ms^{-1}\)

Recall, \(F = mass \times acceleration \implies acceleration = \frac{force}{mass}\)

= \(\frac{10i + 4j}{2} = (5i + 2j) ms^{-2}\)

= \(v = u + at  \implies v \text{at 3 seconds} = 0 + (5i + 2j \times 3)\)

= \((15i + 6j) ms^{-1}\)

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