Misconceptions about incline speed for nonlinear slopes.

In 3 experiments, college students provided qualitative predictions about a marble's speed along nonlinear inclines. When predicting the outcome of a race between identical marbles along differently shaped ramps, most students predicted incorrectly that the shorter path was necessarily quicker (the shorter-quicker belief). When comparing instantaneous speed at 2 points, most students predicted incorrectly that incline speed depended on the slope at that point (the slope-speed belief). A final experiment provides evidence that the slope-speed belief reflects a deeper fallacy regarding the resistance encountered while traversing inclines and lifting objects. This fallacy also predicts the prevalent belief that heavier objects fall faster than lighter objects during incline descent or free fall.