A1: In practice, the USB specification limits the length of a cable between full speed devices to 5 meters (a little under 16 feet 5 inches). For a low speed device the limit is 3 meters (9 feet 10 inches). Q2: Why can't I use a cable longer than 3 or 5m?
Clouds form when moist, warm rising air cools and expands in the atmosphere. The water vapor in the air condenses to form tiny water droplets which are the basis of clouds.
All of these are examples of water leaving the vapor state in the warm air and condensing into liquid as it is cools. Why do clouds form and why does it rain? Air, even clear air, contains water molecules. Clouds exist in the atmosphere because of rising air. As air rises and cools the water in it can condense out, forming clouds. Since clouds drift over the landscape, they are one of the ways that water moves geographically around the globe in the water cycle.