MADISON — They call themselves Infinite Velocity and they’re on their way to Destination Imagination’s Global Finals in Knoxville, Tennessee, billed as the world’s largest celebration of student creativity. And they’re all home-schooled. The group of five middle-school-age students, members of the Somerset Homeschool Co-op, came up with a physics challenge that uses an ordinary power drill, pulleys and rope to haul a box on dolly wheels across the room.