Question 122291
If you set up a free body diagram and look at the forces acting on the particle. 
Let x be the axis parallel to the plane.
Let y be the axis perpendicular to the plane. 
The forces in the x direction are dynamic friction resisting motion and the gravity component assisting motion. 
The forces in the y direction are the gravity component in that direction and the normal force of the table pushing up on the particle. 
The dynamic friction is a function of the gravity component in the y direction.
Force balance in x direction : 1.{{{ma = F[x,g]-F[f]}}}
Force balance in y direction : 2.{{{0=F[N]-F[y,g]}}}
where 
{{{F[x,g]=mg sin(alpha)}}}
{{{F[y,g]=mg cos(alpha)}}}
{{{F[f]= (mu)F[N]=(mu) mg cos(alpha)}}}
{{{m}}} = Mass
{{{g}}} = Gravitational constant
{{{(mu)}}}= Coefficient of friction
{{{(alpha)}}}= Angle of incline

1.{{{ma = F[x,g]-F[f]}}}
{{{ma=mg sin(alpha)-(mu) mg cos(alpha)}}}
{{{ma-mg sin(alpha)=-(mu) mg cos(alpha)}}}
{{{(-ma+mg sin(alpha))/(mg cos(alpha))=(mu)}}}
{{{(mu)=(mg sin(alpha)-ma)/(mg cos(alpha))}}}
{{{(mu)=(2(9.8) sin(20)-2(1.5))/(2(9.8) cos(20))}}}
{{{(mu)=(2(9.8) (0.342)-2(1.5))/(2(9.8) (0.937))}}}
{{{(mu)=(6.7032-3.0)/(18.3652)}}}
{{{(mu)=0.20}}}