Horizontal vs Vertical Surfaces with Friction
When pushing an object such as a book across a horizontal surface such as a table, my book says the following:
μ = Ff/FN
where:
μ: coefficient of friction
Ff: force of friction
FN: Normal force
I understand the above very well but my book did not explain how friction acts along a vertical surface. Let's say I scrapped a rock on a brick wall or something, how would I determine the normal force?
I ask because my book says that FN = Fg = m*g if the surface is horizontal. I understand that perfectly but how would I find the value of FN mathematically if the object was fighting friction on a vertical surface?
Any help would be greatly appreciated!
Thanks in advance!
