Question

A 3kg box slides down a 30.0 degree ramp with an acceleration of 1.4 m/sec^2. Determine the coefficient of kinetic friction between the box and the ramp.

Answer 1

Let's write the Second Newton's Law for the box:
mg sin(30) - μ N = ma
N = mg cos(30);
mg sin(30) - μ mg cos(30) = ma;
μ = (g sin(30) -a )/(g cos(30)) = 0.41