A constant force F = (3i + 7j - 5k) N acts on a particle. The particle moves from point P1 = (1, 2, 3) m to point P2 = (4, -5, -6) m. Find the work done W (in joules). The value of W is:

5 J
-5 J
14 J
-14 J

Correct answer: 5 J

Solution

Displacement d = (4-1)i + (-5-2)j + (-6-3)k = 3i - 7j - 9k m. Work W = F * d = (3)(3) + (7)(-7) + (-5)(-9) = 9 - 49 + 45 = 5 J. Note: the original question listed negative options (-48, -51, -54, -57) which do not match the given force and displacement vectors; the correct calculated value is +5 J.

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