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WAEC Further Mathematics 2007 Question 16

Question 16

Dynamics

Two bodies of masses 8 kg and 5 kg travelling in the same direction with speeds of x ms−1 and 2 ms−1 respectively collide. If after collision, they move together with a speed of 3.85 ms−1 find, correct to the nearest whole number the value of x.

  1. A.2
  2. B.5
  3. C.8
  4. D.13
Show the answer and explanation

Answer: B (5)

Explanation

Momentum is conserved: 8x + 5(2) = 13 × 3.85 = 50.05, so 8x = 40.05 and x ≈ 5.