Forces: Inclined Planes - Solving Problems with Rotated Coordinate Systems

For this mini-lecture, we discuss why we may choose a coordinate system other than the traditional one with y or z as the vertical axis and x as a horizontal axis. We use the example of a box sliding down an inclined plane, against kinetic friction. Aligning a coordinate system with the slope and perpendicular to the slope, we break up the vector from the force of gravity into components in that system. From their we determine relationships between the forces, angles, and acceleration by using Newton's Second Law of motion.