Seen in the hands of Joseph Black in the portrait gallery in Edinburgh ... This piece of equipment is why the name of the video channel on the Internet is a clever physics joke for those in the know. A u-tube usually contains a fluid like water. It can be used as a manometer to measure gas pressure by connecting one end of the u-tube to the gas and leaving the other end open to the atmosphere. If the gas has a pressure higher than that of the atmosphere, the liquid moves round to the atmosphere side. Vice versa if the situation is reversed. Or a u-tube of water with nothing attached can be shown to exhibit simple harmonic motion if the water is displaced to one side and allowed to oscillate.
