Physics (Mechanics)
posted by Anonymous .
A 10kg crate on a ramp is inclined at 30 degrees from the horizontal and released. The coefficients of friction between them are .48 (coefficient of static friction) and .28 (coefficient of kinetic friction).
a) Does the block slide?
b) What then is the actual friction force?
I'm a little confused on this so any help would be greatly appreciated.

component of gravity force down ramp =10*9.8*sin 30
= 49 N
component of gravity force normal to ramp = 10*9.8*cos 30
=84.9 N
Max static friction force = .48*84.9 = 40.7 N
so
gravity wins, it slides and friction coef becomes .28
friction force then = .28*84.9 = 23.8 N