One of the five great simple machines, the WHEEL and axle greatly increased the load that a human or animal could pull by lowering the resistance to movement. The WHEEL was also quickly turned into a weapon of war after its invention, especially in the adaptation of the Chariot. In addition to its use in transport, the WHEEL became a vitally important tool in ENGINEERING and in the Industrial Age. In the pre-Columbian New World, the WHEEL only appeared in children's toys, partly because the mountainous terrain of South America made it less practical.
