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.
This is cloud. They are usually white by irregular reflection . Rain cloud is dark because their water drops are rather large and less transparent. There are many chances when cloud is formed. For example towering thundercloud is formed when air rises high up in the sky. ( I am Japanese and I am afraid my answer may be difficult to understand and contain grammatical errors.) Source(s):