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JAMB Physics 1999 Question 3

Question 3

Work, Energy and Power

A ball of mass 0.1 kg is thrown vertically upwards with a speed of 10 m s−1 from the top of a tower 10 m high. Neglecting air resistance, its total energy just before hitting the ground is [g = 10 m s−2]

  1. A.5 J
  2. B.10 J
  3. C.15 J
  4. D.20 J
Show the answer and explanation

Answer: C (15 J)

Explanation

Total energy is conserved, so it equals the starting energy: KE ½ × 0.1 × 102 = 5 J plus PE 0.1 × 10 × 10 = 10 J, giving 15 J.