In a certain elaborate roller coaster, the cars are not on tracks but inside a U-shaped track much like a bobsled run. The cars are thus free to swing left and right across the U, climbing the walls as they do so. A student on the ride holds a string with a chunk of metal tied to the free end, with the chunk dangling between his knees as the ride begins. When the car enters a tight left turn, does the chunk swing toward the student's left knee, toward his right knee, or in some other direction? Ignore any friction between cars and track.