A wheel is a circular evice that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load (mass), or performing labour in machines. A wheel, together with an axle overcomes friction by facilitating motion by rolling. In order for wheels to rotate, a moment needs to be applied to the wheel about its axis, either by way of gravity, or by application of another external force. Common examples are found in transport applications. More generally the term is also used for other circular objects that rotate or turn, such as a Ship's wheel, steering wheel and flywheel.