Friction torque
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This image displays an example situation where there is an active frictional torque. The large black vector arrow represents the primary force acting on the bar (the thick black line), causing it to rotate around the gray dot at its opposite end which represents an axle. The large red vector arrow represents the torque caused by the primary force. The small black vector arrow represents the frictional force caused by the bar sliding across the second bar (grey).
Friction torque is the torque caused by the frictional force that occurs when two objects in contact move. Like all torques, it is a rotational force which may be measured newton metres or pounds-feet.
[edit] Engineering
Friction torque can be disruptive in engineering. There are a variety of measures engineers may chose to take to eliminate these disruptions. Ball bearings are an example of an attempt to minimize the friction torque.
[edit] Examples
- When a cyclist applies the brake to his/her forward wheel, the bike tips forwards due to the frictional torque between the wheel and the ground.
- When a golf ball hits the ground it begins to spin in part because of the friction torque applied to the golf ball from the friction between the golf ball and the ground.