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JAMB Physics 1997 Question 4

Question 4

Newton's Laws and Momentum

An arrow of mass 0.1 kg moving with a horizontal velocity of 15 m s−1 is shot into a wooden block of mass 0.4 kg lying at rest on a smooth horizontal surface. Their common velocity after impact is

  1. A.15.0 m s−1
  2. B.7.5 m s−1
  3. C.3.8 m s−1
  4. D.3.0 m s−1
Show the answer and explanation

Answer: D (3.0 m s−1)

Explanation

Momentum is conserved: 0.1 × 15 = (0.1 + 0.4)v, so v = 1.5 ÷ 0.5 = 3.0 m s−1.