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.
Clouds form when moist air rises in a low pressure system. As the water molecules cool, they adhere to particulate matter. After many molecules collect and form a droplet big enough, it's weight can overcome any upward lift from the air below it.