How can an object with a constant velocity have zero net force acting on it? The object is moving, so how could nothing be pushing on it?
This important question is addressed by the concept and the observation of inertia. An object that is free of all external forces continues moving as it was. You don’t have to push on something to keep it moving. That is its nature. Left to itself, an object that’s moving will keep moving in a straight line at a steady pace. That’s ultimately the observation that’s called Newton’s first law of motion. Forces, therefore, don’t cause velocity. Velocity is a matter of history; if an object was already moving that’s what it’s going to tend to keep doing.
What forces cause are changes in velocity. In other words, they cause accelerations. So, if an object happens to be, at the point you are paying attention, moving to your right, at some particular velocity, in the absence of any pushes, that’s what it’s going to keep doing. That is its nature. That’s the observation of behaviors in our universe, without exception. The velocity they have is the velocity they keep. You don’t have to push on them to keep them moving; they do that for free. You have to push on them to bring them to a stop, to speed them up, or to change their direction.