If I were to hold a block against a vertical wall that has a static and kinetic friction coefficient of 0, would the block fall down?
I think that it would fall down because the only force holding it up is the friction force acting against gravity. However, since the coefficients of friction are zero, there will be no friction force, no matter how hard I push the block against the wall.
However, this doesn't make intuitive sense because I'm sure that a block would still stay in place if you pushed it against the wall with a lot of force, no matter how frictionless the wall is.
We are assuming that the wall is rigid and won't deform under the block's pressure.