How many simple machines are in a revolving bridge?

What is the similarties between a dam and a levee? The wheels and gears of a machine are greased in order to decrease? What is glass point of material? What are generally placed along construction sites? How does HTML code produce the form displayed in the browser? What is the difference between plastic and rubber? What equipment is used to mine minerals? How do you implement a deque using an array in c language? What 4 new inventions design or ideas of the 1780s? What are some ways that they have tried to clean the oil spill? What is the material to make printed circuit board? What are the advantages and disadvantages of spiraltube heat exchangers? What do they use for a power source in factories? My HDTV does not fill the screen? What types of transistors are the following - BJT PCT UJT SBT FET GJT AJT DFT? How does a hydraulic gauge work? What is the angle of repose for blast furnace slag? What was John Gorrie's invention called? When was the first hydro dam built? What is the full name of the blackhawk helicopter?