"Object has a kinetic energy : "E_k=1/2*m*v^2 E_k:"The kinetic energy of object" m:"mass of object" v:" velocity of object" "The kinetic energy of object is turned to the heat energy by " "the friction force." E_k=F_f*Delta x 1/2*cancel(m)*v^2=u_k*cancel(m)*g*Delta x Delta x=v^2/(2*u_k*g)