Keisha writes that if an object has any external forces acting on it, then the object can be in dynamic equilibrium but not static equilibrium. Which statement best describes Keisha’s error?

Equilibrium means the net force on an object is zero, not that no forces act on it. Several external forces can balance one another, allowing an object to remain at rest (static equilibrium) or move at constant velocity (dynamic equilibrium). Therefore, Keisha is wrong to rule out static equilibrium whenever external forces are present; the correct statement is that either kind of equilibrium requires no net force.

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