Physics
posted by Amanda .
A crate is sliding down a ramp that is inclined at an angle 37.9 ° above the horizontal. The coefficient of kinetic friction between the crate and the ramp is 0.330. Find the acceleration of the moving crate.

parallel plane: mgsin(39.5)  .330N = ma
perpendicular plane: N  mgcos(39.5) = 0 <== because it is not accelerating perpendicular the plane
so N = mgcos(39.5)
therefore, parallel plane: mgsin(39.5)  .330(mgcos(39.5)) = ma
m's cancel: gsin(39.5)  .33gcos(39.5) = a
a = 3.74 m/s^2