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Ground propulsion is any mechanism for propelling solid bodies along the ground, usually for the purposes of transportation. The propulsion system often consists of a combination of an engine or motor, a gearbox and wheel and axles (or caterpillar tracks) in standard applications. The primary and most natural type of propulsion is the use of muscle power. Vehicles drawn by an animal have nearly disappeared nowadays. There are some communities left, where one can make a living solely relying on the techniques employing muscle energy in a very efficient form like bicycles, wheelchairs etc.. But civilization employs other types of methods to transport bodies with higher velocities, in the last two centuries up into the 1970s mostly steam engines. Now the main focus is on *internal-combustion engines *electric motors (which includes linear motors being part of the track) or combinations of those. Turbines are rarely used because of the small part load efficiency, although land speed record cars do use them. Also other types with external combustion like the Stirling engine or without combustion like the fuel cell are only used in planes. It is different in transmission that has a manual or automatic. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ground propulsion」の詳細全文を読む スポンサード リンク
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