Complete the sentences to describe the difference between static and dynamic equilibrium. an object in equilibrium has a net force static equilibrium describes an object equal and balanced forces acting upon it. dynamic equilibrium describes an object having equal and balanced forces acting upon it.

a) An object in equilibrium has a net force of zero.
- An object is said to be in equilibrium if all the forces acting on the object are balanced, so that the net force (=resultant of the forces) acting on the object is zero.

b) Static equilibrium describes an object at rest having equal and balanced forces acting upon it. 
- An object is said to be in static equilibrium if it is at rest and all the forces acting on the object are balanced, so that the net force (=resultant of the forces) acting on the object is zero. In this case, the object will remain at rest, according to Newton's second law:

where the first term is the resultant of the forces acting on the object, m is its mass and a its acceleration. Since the resultant of the forces is zero, the acceleration is zero as well, and the object will remain at rest.

c) Dynamic equilibrium describes an object in motion having equal and balanced forces acting upon it.
- An object is said to be in dynamic equilibrium if it is in motion and all the forces acting on the object are balanced, so that the net force (=resultant of the forces) acting on the object is zero. In this case, the object will remain in motion with constant velocity, according to Newton's second law:

where the first term is the resultant of the forces acting on the object, m is its mass and a its acceleration. Since the resultant of the forces is zero, the acceleration is zero as well, and the object will not change its velocity.