Newton's First Law
Newton’s First Law:
If the resultant force acting on an object is zero and:
• the object is stationary, the object remains stationary
• the object is moving, the object continues to move at the same speed and in the same direction.
So the object continues to move at the same velocity.
So, when a vehicle travels at a steady speed the resistive forces balance the driving force. So, the velocity (speed and/or direction) of an object will only change if a resultant force is acting on the object.
The tendency of objects to continue in their state of rest or of uniform motion is called inertia.