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Re: [Phys-L] defining inertia ... or not




On 2016, Aug 17, , at 12:46, John Denker <jsd@av8n.com> wrote:


Small point: If you try to measure the coefficient of friction between
two very flat, very clean blocks of metal, you'll find that it's infinite.
The blocks will cold-weld, and you'll never get them apart again.


Johansson blocks are v. slightly dirty, and is it atmospheric pressure?

bc

Wiki’s “take”:

While the exact mechanism that causes wringing is unknown,[5][6] it is believed to be a combination of:[4][5]

• Air pressure applies pressure between the blocks because the air is squeezed out of the joint.
• Surface tension from oil and water vapor that is present between the blocks.
• Molecular attraction occurs when two very flat surfaces are brought into contact. This force causes gauge blocks to adhere even without surface lubricants, and in a vacuum.


https://en.wikipedia.org/wiki/Gauge_block