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Motion (physics)

2007 Schools Wikipedia Selection. Related subjects: General Physics

   Motion involves change in position, such as this perspective of rapidly
   leaving Yongsan Station
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   Motion involves change in position, such as this perspective of rapidly
   leaving Yongsan Station

   In physics, motion means a continuous change in the position of a body
   relative to a reference point, as measured by a particular observer in
   a particular frame of reference. Until the end of the 19th century,
   Newton's laws of motion, which he posited as axioms or postulates in
   his famous Principia, were the basis of what has since become known as
   classical physics. Calculations of trajectories and forces of bodies in
   motion based on Newtonian or classical physics were very successful
   until physicists began to be able to measure and observe very fast
   physical phenomena.

   At very high speeds, the equations of classical physics were not able
   to calculate accurate values. To address these problems, the ideas of
   Henri Poincaré and Albert Einstein concerning the fundamental
   phenomenon of motion were adopted in lieu of Newton's. Whereas Newton's
   laws of motion assumed absolute values of space and time in the
   equations of motion, the model of Einstein and Poincaré, now called the
   special theory of relativity, assumed values for these concepts with
   arbitrary zero points. Because (for example) the special relativity
   equations yielded accurate results at high speeds and Newton's did not,
   the special relativity model is now accepted as explaining bodies in
   motion (when we ignore gravity). However, as a practical matter,
   Newton's equations are much easier to work with than those of special
   relativity and therefore are more often used in applied physics and
   engineering.

   In the newtonian model, because motion is defined as the proportion of
   space to time, these concepts are prior to motion, just as the concept
   of motion itself is prior to force. In other words, the properties of
   space and time determine the nature of motion and the properties of
   motion, in turn, determine the nature of force.

   In the special relativistic model, motion can be thought of as
   something like an angle between a space direction and the time
   direction.

   In special relativity and Euclidean space, only relative motion can be
   measured, and absolute motion is meaningless.

   An object is in motion when its distance from another object is
   changing.Whether the object is moving or not depends on your point of
   view. For example, a woman riding in a bus is not moving in relation to
   the seat she is sitting on, but she is moving in relation to the
   buildings the bus passes. A reference point is a place or object used
   for comparison to determine if something is in motion. An object is in
   motion if it changes position relative to a reference point. You assume
   that the reference point is stationary, or not moving.

   Kinematics

   ← Integrate ... Differentiate →
   Displacement | Velocity ( Speed) | Acceleration | Jerk | Snap

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