* Newton's First Law of Motion (Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

* Net Force: The overall force acting on an object. If the forces are balanced, the net force is zero.

Scenario: Imagine a car moving at a constant speed on a straight, level road. Here's what's happening:

* Forces Acting:

* Forward force: The engine provides a force pushing the car forward.

* Friction: Air resistance and friction from the tires and road oppose the forward motion.

* Balanced Forces: If the forward force from the engine exactly balances the opposing forces of friction, the net force is zero.

* Constant Velocity: Since the net force is zero, the car continues moving at a constant speed in a straight line.

In summary: An object can be moving at a constant velocity (constant speed and direction) even if the net force acting on it is zero. This happens when all the forces acting on the object are perfectly balanced.