A block with initial velocity of 3 m/s slides 9 m across a rough horizontal surface before coming to rest. What is the coefficient of kinetic friction?

##k~=0051##
##if object stops velocity of object is zero.##
##v_l: last velocity of object##
##v_i: initial velocity of object##
##a: acceleration of object##
##x: displacement of object##
##F_f: friction force acting contacting surface##
##k: coefficient of kinetic friction##
##v_l^2=v_i^2-2.a.x##
##0=3^2-2*a*9##
##cancel(9)=2*a*cancel(9)##
##a=1/2 m/s^2##
##F_f=m*a##
##k*cancel(m)*g=cancel(m)*a##
##k=a/g##
##k=(05)/(981)##
##k~=0051##