I was just looking up something about Uranus on Google, and read a line I had read many times before - "The strong winds of Uranus...". So, short and easy - "What causes the strong winds on Uranus?".
As said, winds on Uranus are quite strong blowing upto 560 miles/hr (900 kmph). But, the question is what forces drives these winds?
Researchers has been digging for quite a while. They investigated the gravity fields of Uranus using data gathered by NASA's Voyager 2 spacecraft and ground-based telescopes. The strength of a planet's gravity field depends on its amount of mass, and this strength can vary over the surface of a planet depending on the amount of mass lying under it. By analyzing the gravity fields of these worlds, the investigators could deduce how their atmospheres circulated. From the readings, they deduced that the winds blow in relatively thin weather layers no more than 600 miles (1,000 kilometers) but comparing to size of Uranus, the layers are proportionally very small (0.15 % of the mass of Uranus). So, the researchers propose that the winds are mostly driven by atmospheric and surface conditions (possibly moisture evaporating and condensing in atmosphere causing the winds to swirl).
Some suggest that since the outer planets are gaseous, there is virtually no surface roughness to act as a drag on winds like on Earth and hence the atmospheres is more fluid like. Moreover, Uranus is very far away from the sun and thus there is less solar energy to impact the turbulence in the atmosphere.
Some also suggests internal heat to be the reason. Uranus only puts out about 6 percent as much heat as it receives from the Sun. So, internal heat source might be involved on some level.
For more information, read this excellent paper: Atmospheric confinement of jet streams on Uranus and Neptune