A ball falls from a height of 18m above the ground. Find the speed with which the ball hits the ground. \([g = 10ms^{-2}]\)

  • A 9\(ms^{-1}\)
  • B 9.49\(ms^{-1}\)
  • C 13.42\(ms^{-1}\)
  • D 18.97\(ms^{-1}\)
waec 2016furthermathematics

The correct answer is D. 18.97\(ms^{-1}\)

Due to conservation of energy, K.E = P.E

\(\frac{1}{2}mv^{2} = mgh\)

\(\implies m \times 10 \times 18 = \frac{1}{2}mv^{2}\)

\(v^{2} = 2 \times 10 \times 18 = 360\)

\(v = \sqrt{360} = 18.97ms^{-1}\)

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