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WAEC Further Mathematics 2013 Question 26

Question 26

Dynamics

Two bodies of masses 3kg and 5kg moving with velocities 2 ms−1 and V ms−1 respectively in opposite directions collide. If they move together after collision with velocity 3.5 ms−1 in the direction of the 5kg mass, find the value of V.

  1. A.7.8 ms−1
  2. B.6.8 ms−1
  3. C.5.6 ms−1
  4. D.4.6 ms−1
Show the answer and explanation

Answer: B (6.8 ms−1)

Explanation

Taking the 3 kg body's direction as positive: 3(2) − 5V = 8(−3.5), so 6 − 5V = −28 and V = 6.8.