The first condition of equilibrium requires that

  • A. the vector sum of all forces acting on the body is zero
  • B. the sum of all torques about any point is zero
  • C. the body is at rest
  • D. no force acts on the body at all

Explanation

With zero net force there is no acceleration of the centre of mass, which is translational equilibrium. The second condition deals with rotation and requires zero net torque, and a body needs both to be in complete equilibrium. Note that equilibrium allows motion at constant velocity, so being at rest is not required.

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