A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, torque, and direction of a power source. The most common situation is for a gear to mesh with another gear, however a gear can also mesh a non-rotating toothed part, called a rack, thereby producing translation instead of rotation.

The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that the teeth of a gear prevent slipping.

When two gears of unequal number of teeth are combined a mechanical advantage is produced, with both the rotational speeds and the torques of the two gears differing in a simple relationship.

In transmissions which offer multiple gear ratios, such as bicycles and cars, the term gear, as in first gear, refers to a gear ratio rather than an actual physical gear. The term is used to describe similar devices even when gear ratio is continuous rather than discrete, or when the device does not actually contain any gears, as in a continuously variable transmission.

Ken Block (born November 21, 1967, in Long Beach, California) is a professional rally driver with the Monster World Rally Team. Block is also one of the co-founders and recently appointed Chief Brand Officer of DC Shoes. Block has also competed in many action sports events including skateboarding, snowboarding, and motocross.

In 2005, Ken Block began his national rallying career with the Vermont SportsCar team. Vermont SportsCar prepared a 2005 Subaru WRX STi for Block to compete. His first event of the rallying season was Sno*Drift, where he ended up finishing seventh overall and fifth in the Group N class. During the 2005 season, Block had five top five finishes and placed third overall in the Group N class and fourth overall in the Rally America National Championship. At the end of his first rallying year, Ken Block had won the Rally America Rookie of the Year award.

In 2006, Ken Block along with his DC rally teammate Travis Pastrana signed a new sponsorship deal with Subaru. Through this deal with Subaru, the teammates became known as "Subaru Rally Team USA." With the new rally season, Block also got a brand new Vermont SportsCar prepped 2006 Subaru WRX STi. He competed in the first ever X Games rally event at X Games XII. In the competition, Block ended up finishing third to take the bronze. He went on to compete in the 2006 Rally America National Championship, where he finished second overall.

Lewis Carl Davidson Hamilton,MBE (born 7 January 1985) is a British Formula One racing driver from England, currently racing for the McLaren team. He is the 2008 Formula One World Champion.

Hamilton was born in Stevenage, Hertfordshire. In December 1995, at the age of ten, he approached McLaren team principal Ron Dennis at the Autosport Awards ceremony and told him, "I want to race for you one day ... I want to race for McLaren." Less than three years later McLaren and Mercedes-Benz signed him to their Young Driver Support Programme. After winning the British Formula Renault, Formula Three Euroseries, and GP2 championships on his way up the racing career ladder, he drove for McLaren in 2007, making his Formula One debut 12 years after his initial encounter with Dennis. Lewis Hamilton's contract for the McLaren driver development program made him the youngest ever driver to secure a contract which later resulted in an F1 drive.

Coming from a mixed-race background, with a black father and white mother, Hamilton is often labelled "the first black driver in Formula One", although Willy T. Ribbs tested an F1 car in 1986. He is also the first driver of black heritage to win a major race at Indianapolis Motor Speedway in any discipline.