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Post by the light works on Dec 25, 2018 4:32:57 GMT
it's pretty simple math - more surface area = more friction. but is there a point of diminishing returns where more surface area results in less presure between the surfaces, and thus LESS friction?
the idea came to me as the dog was having to work to keep position lying on the car seat, whereas she had no trouble sitting in a seat.
it could also be the seat material or the shape of the seat - but it might be a good subject for testing - and I'm curious if my logic is valid.
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Post by GTCGreg on Dec 25, 2018 6:10:31 GMT
If I remember correctly from my collage physics days, if the coefficient of friction of the two materials remains constant, the surface area cancels out with the change in surface pressure. But in the real world, the surface interface can deform with pressure and the coefficient of friction can actually change with pressure. Thus the surface area can become a deciding factor.
In the case of your dog, it could also be the the dogs front paws and rear end have a higher coefficient of friction than the dogs belly laying on the seat. Also when sitting, the dog becomes an active load, being able to shift its pressure points to compensate for changes in acceleration of the vehicle.
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Post by the light works on Dec 25, 2018 15:19:47 GMT
If I remember correctly from my collage physics days, if the coefficient of friction of the two materials remains constant, the surface area cancels out with the change in surface pressure. But in the real world, the surface interface can deform with pressure and the coefficient of friction can actually change with pressure. Thus the surface area can become a deciding factor. In the case of your dog, it could also be the the dogs front paws and rear end have a higher coefficient of friction than the dogs belly laying on the seat. Also when sitting, the dog becomes an active load, being able to shift its pressure points to compensate for changes in acceleration of the vehicle. I was, of course, thinking real world, rather than college classroom world. I recall there was a thread on the old disco boards that claimed the contact patch of a tire was solely dependant on inflation pressure rather than on tire size. so bigger tires did not give more traction. of course, it was pointed out that this would only be valid in a balloon tire which supported the load ONLY with air pressure, while real world tires use sidewall stiffness to help support the load, and the shaping of the carcass affects the width of the contact patch; s well as the compression of the rubber. |
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