1. The problem statement, all variables and given/known data What can be said about a car traveling at constant velocity on a street, keeping in mind newton's first law? 2. Relevant equations 3. The attempt at a solution My first reaction to this question is "But a car is not a particle." Assuming the car is a particle, then it must be safe to say that the car is some how over coming all the forces of friction in order to stay at a constant speed. When I think of something moving at a constant speed without forces acting on it, I think of a ball floating in outer space. So I feel like I am overlooking something, like, perhaps, that even though the car is traveling at a constant velocity, the sum of the forces acting on it is not zero: The weight of the car is balanced by the normal force, but the friction acting on the tires isn't balanced by any external force; an internal force is counteracting the friction, so it seems to me that it would be more accurate to say that newton's first law doesn't apply to this situation.