Previous studies have shown that many adults have striking misconceptions about the motions of objects in seemingly simple situations. The present two studies explored the development of knowledge about motion by examining children’s predictions about the movement of an object in two types of situations. In one type of situation, children predicted where a ball would land if it rolled off the edge of a table and fell to the floor. In the other type of situation, children judged where the same ball would land if it were dropped from a moving model train and fell the same distance to the floor. Younger children (preschool and kindergarten) generally thought that the ball would fall straight down in both situations. At older ages, children were more aware that the ball rolling from the table would continue to move forward while falling. For the ball dropped from the train, however, the older children were no more aware of the ball’s forward motion than were younger children. The results are interpreted in terms of general cognitive capabilities and perceptual experiences that contribute to the development of knowledge about the world.