I went to a christening down south. There had been a service before hand and the air was heavy with incense. Looking up I saw was reminded that light travels in straight lines! It's like using a little milk in water to show up a laser beam.
The font had a heavy carved wooden cover on it. You might be wondering how it comes to be hovering in mid-air in this photograph.
The answer will lie in the metal cross shown in this photograph. I would imagine that it will have the same weight as the wooden font cover. They are at opposite ends of a chain which hangs over a pulley. When one goes up, the other must come down. Hence as you do work lifting the font cover, gravity does work on the cross to lower it. The only energy needed in the system is that required to overcome the friction of the chain and the pulley. It becomes easy to lift the heavy wooden cover.
