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A fictitious force, also called a pseudo force, d'Alembert force or inertial force,〔(NASA notes:(23) Accelerated Frames of Reference: Inertial Forces )〕 is an apparent force that acts on all masses whose motion is described using a non-inertial frame of reference, such as a rotating reference frame. The force F does not arise from any physical interaction between two objects, but rather from the acceleration a of the non-inertial reference frame itself. As stated by Iro:〔In this connection, it may be noted that a change in coordinate system, for example, from Cartesian to polar, if implemented without any change in relative motion, does not cause the appearance of fictitious forces, despite the fact that the form of the laws of motion varies from one type of curvilinear coordinate system to another.〕 Assuming Newton's second law in the form F = ''m''a, fictitious forces are always proportional to the mass ''m''. A fictitious force on an object arises when the frame of reference used to describe the object's motion is accelerating compared to a non-accelerating frame. As a frame can accelerate in any arbitrary way, so can fictitious forces be as arbitrary (but only in direct response to the acceleration of the frame). However, four fictitious forces are defined for frames accelerated in commonly occurring ways: one caused by any relative acceleration of the origin in a straight line (rectilinear acceleration);〔The term ''d'Alembert force'' often is limited to this case. See Lanczos, for example.〕 two involving rotation: centrifugal force and Coriolis force; and a fourth, called the Euler force, caused by a variable rate of rotation, should that occur. Gravitational force would also be a fictitious force based upon a field model in which particles distort spacetime due to their mass. ==Background== The role of fictitious forces in Newtonian mechanics is described by Tonnelat: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fictitious force」の詳細全文を読む スポンサード リンク
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