Monday, 7 January 2019

newtonian mechanics - What is the cause of rolling friction? & why is it less than sliding friction?



Rolling friction is the resistance to motion experienced by a body when it rolls upon another. It is much less than sliding friction for same pair of bodies. When one body rolls upon another, there is theoretically no sliding or slip between them. And if both are perfectly rigid, there is no surface of contact.



Then the book writes:



Different causes are present depending on the nature of the wheel and the road. For a hard wheel on a soft dirty road, as the road is slightly depressed at the point of contact and a ridge is formed in front of the wheel. Thus, the wheel is being continuously pulled up in a minute hill which causes rolling friction.




Now, my questions are: - How does the ridge provide rolling friction in the opposite direction of rolling? - There is not always soft road. What happens in the hard road? - Why is rolling friction less than sliding friction??


Please help.




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