Express the force F = (8 N, 150°) in the form (a i + b

FURTHER MATHEMATICSWAEC 2009

Express the force F = (8 N, 150°) in the form (a i + b j) where a and b are constants.

  • A. \(4\sqrt{3} i - 4j\)
  • B. \(4 i - 4\sqrt{3} j\)
  • C. \(- 4 i + 4\sqrt{3} j\)
  • D. \(- 4\sqrt{3} i + 4j\)

Correct Answer: D. \(- 4\sqrt{3} i + 4j\)

Explanation

\(F = F\cos \theta i + F \sin \theta j\)

\((8 N, 150°) = 8 \cos 150 i + 8 \sin 150 j\)

= \(- 8 \cos 30 i + 8 \sin 30 j\)

= \(-8(\frac{\sqrt{3}}{2}) i + 8(\frac{1}{2} j\)

= \(-4\sqrt{3} i + 4 j\)

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