The minimum number of unequal coplanar forces whose vector sum can be zero is

  • A. one
  • B. two
  • C. three
  • D. four

Explanation

Two unequal forces can never cancel, since cancelling requires equal magnitudes in opposite directions. Three forces can close a triangle head to tail even when all three magnitudes differ, so three is the minimum. This is why the triangle of forces is the standard construction for a body in equilibrium under three forces.

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