A skateboarder is moving down a ramp and reaches the bottom with a specific velocity. Assuming negligible friction and air resistance, which principle would best describe the skateboarder's motion as they transition from potential energy at the top of the ramp to kinetic energy at the bottom?

The skateboarder’s motion is governed by the conservation of mechanical energy: the loss of gravitational potential energy as he descends the ramp is converted into kinetic energy. Because friction and air resistance are negligible, the total mechanical energy stays constant. Thus, at the bottom the kinetic energy equals the initial potential energy, giving his velocity. For example, a 2‑meter high ramp gives a potential energy of \(mgh\); this becomes \(\tfrac12 mv^2\) at the bottom, so \(v=\sqrt{2gh}\). This principle explains how the skateboarder speeds up while moving down.