An 18.8kg box is released on a 38.0o incline and accelerates down the incline at 0.281m/s2. What is the magnitude of the friction force impeding its motion.
F = m*g*cos(38)
sum forces parallel to the plane
m*g*sin(38) - (mu)*(F) = m*a, or
m*g*sin(38) - (mu)*m*g*cos(38) = m*a
masses cancel...