ocr: Why is it hard to keep things moving? A moving object encounters tWO types of frictional force that slow it down. The first force is the triction between the moving object and the surface it is moving over. The second force is air friction, or drag, which becomes greater the faster the object is moving. One object can move past another in tWo different ways: it can slide like a sled or it can roll like a ball. In general, its easier to roll an object than to slide it.
(.png)
