Under what condition is the work done by a constant force on a moving particle equal to zero?
Answer and explanation
Correct answer: B. When the force is perpendicular to the displacement vector (theta = 90°)
- Step 1: Work formula: W = F d cos(theta). Step 2. When theta = 90 degrees, cos(90°) = 0, so W = 0. A classic example is uniform circular motion where the centripetal force is always perpendicular to instantaneous velocity. Answer: When the force is perpendicular to the displacement vector (theta = 90°). Why not the others: Opposite directions yield negative work (W = -F*d); straight-line acceleration involves non-zero work.
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