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WAEC Further Mathematics 2020 Question 37

Question 37

Vectors

Find the unit vector in the direction opposite to the resultant of forces F1 = (−2i − 3j) and F2 = (5i − j).

  1. A.⅕(−3i − 4j)
  2. B.⅕(−3i + 4j)
  3. C.⅕(3i − 4j)
  4. D.⅕(3i + 4j)
Show the answer and explanation

Answer: B (⅕(−3i + 4j))

Explanation

The resultant is 3i − 4j, of length 5. The opposite direction is −3i + 4j, so the unit vector is ⅕(−3i + 4j).