In an experiment, an inclined plane is set up. A 200 g mass is placed on a car, and the car is placed at the bottom of the inclined plane. The object is to find the correct hanging weight that will allow the car to move up the plane with constant velocity once it has been started. My question: Why should F(w) [the weight of the mass of the car being raised in each trial] be moving with constant velocity in each trial?