Whether you call them pulleys, sheaves, or blocks, these ancient devices make light work of heavy loads. A single pulley can cut the amount of force needed to lift an object in half. Multiple pulleys threaded with rope or wire, known as block and tackle, can reduce the energy required to hoist an object into the air even more. Strictly speaking, the blocks of a pulley are the wood, bronze, brass, or cast-iron pieces that sandwich the...Continue Reading