{{Unreferenced, date=January 2008 In

mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objects r ...

, friction torque is the

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

caused by the

frictional force Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

that occurs when two objects in contact move. Like all torques, it is a rotational force that may be measured in

newton meter The newton-metre (also newton metre or newton meter; symbol N⋅m or N m) is the unit of torque (also called ) in the International System of Units (SI). One newton-metre is equal to the torque resulting from a force of one newton applie ...

s or pounds-feet.

Engineering

Friction torque can be disruptive in

engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

. There are a variety of measures

engineers Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the limit ...

may choose to take to eliminate these disruptions.

Ball bearings A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this ...

are an example of an attempt to minimize the friction torque. Friction torque can also be an asset in engineering. Bolts and nuts, or screws are often designed to be fastened with a given amount of torque, where the friction is adequate during use or operation for the bolt, nut, or screw to remain safely fastened. This is true with such applications as lug nuts retaining wheels to vehicles, or equipment subjected to vibration with sufficiently well-attached bolts, nuts, or screws to prevent the vibration from shaking them loose.

Examples

*When a cyclist applies the brake to the forward wheel, the bicycle tips forward 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.

Engineering

Examples

See also