Final answer:
An object in equilibrium has a net force of zero, whether it is in static equilibrium at rest or dynamic equilibrium while moving at a constant velocity. The main difference is that static equilibrium involves no movement, while dynamic equilibrium involves constant velocity movement.
Step-by-step explanation:
An object in equilibrium has a net force of zero. This is true for both static and dynamic equilibrium in physics. Static equilibrium occurs when an object is at rest and there is no net force causing any movement. This means all the forces that are acting on the body are completely balanced. An example of static equilibrium is a desk sitting still on the floor, not moving, and subject to no net external forces or torques.
In contrast, dynamic equilibrium happens when an object is moving at a constant velocity and is not accelerating. This also implies that the net external force acting on the object is zero, even though it is in motion. For example, a car traveling at constant speed on a straight road experiences dynamic equilibrium because the forces, like engine propulsion and air resistance, are balanced.
Therefore, the main difference between static and dynamic equilibrium is that static equilibrium involves objects at rest, while dynamic equilibrium involves objects moving at a constant velocity, with no acceleration in either case.