Alright, I have another question that I want to make sure I did correct. The question is "an objec of mass m is at rest on a rough inclined plane with height h, lenght 8 m, and which makes an angle of 30degrees with the horizontal. The object is allowed to move and it stops on a rough horizontal surface, at a distance of 4m from the botton of the inclined plane as shown. The coefficient of kinetic friction on the inclined plane is 0.4 and g=10m/s^2. What is the speed of the object ast the bottom of the inclined plane? Alright i used the equation KEfinal -PEfinal = KEinitial -PEinitial, put in the numbers and calculated the velocity to be 12.65 m/s. The second questin is... What is the coefficient of kinetic friction for the horizontal surface? I used the equation Normal force = Force of weight and got mass*gravity*distance *coefficient of kinetic friction = mass*gravity*distance*coefficient of friction on the incline. I cancelled the mass and the gravity and put in the numbers, (4m for distance on horizontal0*(uk)= distance of 4 m, (which i obtained from sin30=8/d)*cos30degrees*0.4(the planes coefficient of friction). I then solved for the coefficient of fricton from the horizontal and calculated 0.35. (Is this correct?