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JAMB Physics 1981 Question 33

Question 33

Motion

A body falls freely under gravity (g = 9.8 m s−2) from a height of 40 m on to the top of a platform 0.8 m above the ground. Its velocity on reaching the platform is

  1. A.784 m s−1
  2. B.80 m s−1
  3. C.78.4 m s−1
  4. D.39.2 m s−1
  5. E.27.7 m s−1.
Show the answer and explanation

Answer: E (27.7 m s−1.)

Explanation

It falls 40 − 0.8 = 39.2 m. v² = 2gh = 2 × 9.8 × 39.2 = 768.3, so v ≈ 27.7 m s−1.