It is common in introductory physics to show that in the absence of air drag an object dropped from rest will reach the level ground at exactly the same time as one that is projected horizontally from the same height. However, the situation is different in the presence of a speed-dependent drag force, as either object may hit first or they may hit at the same time. Drag force is quite complex, and the dependence of the drag force on speed is related to a number of factors, some of which are beyond the scope of this paper. Here we specifically discuss the cases of drag forces with a magnitude dependent on an integer power (2, 1, and 0) of the speed v, as these are suitable for study in introductory courses.

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