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A body has zero net force acting on it, but the net moment of forces about some axis is nonzero. Which statement is correct?
AThe body is in complete equilibrium
BThe body is in rotational equilibrium but not translational equilibrium
CThe body is in translational equilibrium but not rotational equilibrium
DThe body must remain permanently at rest
Answer & Solution
Correct answer: C. The body is in translational equilibrium but not rotational equilibrium
Equilibrium has two parts: translational equilibrium requires $\vec F_{\text{net}}=0$, and rotational equilibrium requires zero net moment. Here the net force is zero, so there is no linear acceleration, but the nonzero moment can still cause rotation. Hence the body is only in translational equilibrium, not complete equilibrium.
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