Imagine a skateboarder rolling down a hill. Draw a force diagram of the skateboarder. Assume for now that there is no friction between the skateboard and the hill. Try to add two more force vectors to your force diagram that break the force of gravity into components parallel to and perpendicular to the ramp surface. Add second a force to your force diagram, this time directed parallel to the ramp surface but pointed up the ramp. Make the magnitude of the force such that it that would cause the skateboarder to move with constant velocity.