Leonardo da Vinci is usually credited with conducting the first systematic study of friction in the late 15th century, a subfield now known as tribology that deals with the dynamics of interacting surfaces in relative motion. Da Vinci's notebooks depict how he pulled rows of blocks using weights and pulleys, an approach that is still used in frictional studies today, as well as examining the friction produced in screw threads, wheels, and axles. The authors of this latest paper used an experimental setup similar to da Vinci's.
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Beth Gardiner is right to argue that plastic is not merely a recycling failure (‘They pushed so many lies about recycling’: the fight to stop big oil pumping billions more into plastics, 19 February). It is something far more consequential: an oil growth strategy.
“党中央高度重视‘三农’工作，一定会采取切实有力的政策举措，回应老百姓的关切和需求，把乡村振兴的美好蓝图变为现实。”习近平总书记的承诺字字铿锵。