I have a question regarding the Rolling Motion equation. [tex](1/2)Mv^2 + (1/2)I\omega^2 + Mgy[/tex] (Where M=mass, v=velocity, I=moment of inertia,ω=angular velocity, g=force due to gravity and y = vertical distance) The problem I'm having involves the direction of the acceleration due to gravity. I've seen the equation written as... [tex](1/2)Mv^2 + (1/2)I\omega^2 = Mgy[/tex] Are they assuming acceleration due to gravity is downward? Hence, adding Mgy to both sides to produce the above results? I guess the problem I'm having is distinguishing when to make the acceleration due to gravity positive/negative (in Work/Energy related problems).