frame of reference

(noun)

A coordinate system or set of axes within which to measure the position, orientation, and other properties of objects in it.

Related Terms

Examples of frame of reference in the following topics:

  • Reference Frames and Displacement

    • This is referred to as choosing a coordinate system, or choosing a frame of reference.
    • In this classic film, Professors Hume and Ivey cleverly illustrate reference frames and distinguish between fixed and moving frames of reference.
    • Displacement is the change in position of an object relative to its reference frame.
    • shows the importance of using a frame of reference when describing the displacement of a passenger on an airplane.
    • Frames of Reference is a 1960 educational film by Physical Sciences Study Committee.

  • The Coriolois Force

    • The Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame.
    • The Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame.
    • Newton's laws of motion govern the motion of an object in a (non-accelerating) inertial frame of reference.
    • When Newton's laws are transformed to a uniformly rotating frame of reference, the Coriolis and centrifugal forces appear.
    • In the inertial frame of reference (upper part of the picture), the black object moves in a straight line.

  • Relative Velocity

    • The concept of relative velocity has to do with your frame of reference.
    • When you were on the train, your frame of reference was moving in the same direction that the man was walking, so it appeared that he was walking slower.
    • But once you were off the train, you were in a stationary frame of reference, so you were able to observe him moving at his actual speed.
    • When you were on the boat, you were in a moving frame of reference, but so was the object you were observing, so you were able to observe the man walking at his actual velocity.
    • Once you were back on land, you were in a stationary frame of reference, but the man was not, so the velocity you saw was his relative velocity.

  • Length Contraction

    • Length contraction arises due to the fact that the speed of light in a vacuum is constant in any frame of reference.
    • We have established that in a frame of reference that is moving relative to the clock (the stationary observer is moving in the clock's frame of reference), the clock appears to run more slowly.
    • You can mathematically determine the length of the ruler in your frame of reference (L') by multiplying your velocity (v) by the time that you perceive that it takes you to pass by the ruler (t').
    • Just as in the clock explanation, the ruler appears to be moving in your frame of reference, so t will be longer than t' (your time interval).
    • Consequently, the length of the ruler will appear to be shorter in your frame of reference (the phenomenon of length contraction occurred).

  • Einstein's Postulates

    • In the late 19th century, the Newtonian mechanics was considered to be valid in all inertial frames of reference, which are moving at a constant relative velocity with respect to each other.
    • In his "Special Theory of Relativity," Einstein resolved the puzzle and broadened the scope of the invariance to extend the validity of all physical laws, including electromagnetic theory, to all inertial frames of reference.
    • The Principle of Relativity: The laws of physics are the same and can be stated in their simplest form in all inertial frames of reference.
    • This postulate relates to reference frames.
    • The laws of electricity and magnetism predict that light travels at c = 2.998×108 m/s in a vacuum, but they do not specify the frame of reference in which light has this speed.

  • Simultaneity

    • The relativity of simultaneity is the concept that simultaneity is not absolute, but depends on the observer's reference frame.
    • The relativity of simultaneity is the concept that simultaneity–whether two events occur at the same time–is not absolute, but depends on the observer's frame of reference.
    • "event A causes event B" in all frames of reference).
    • Reference frame of an observer standing on the platform (length contraction not depicted).
    • The train-and-platform experiment from the reference frame of an observer onboard the train.

  • Relativistic Momentum

    • It also results in a prediction that the speed of light can vary from one reference frame to another.
    • In the theory of special relativity, Albert Einstein keeps the postulate that the equations of motion do not depend on the reference frame, but assumes that the speed of light c is invariant.
    • As a result, position and time in two reference frames are related by the Lorentz transformation instead of the Galilean transformation.
    • Consider, for example, a reference frame moving relative to another at velocity v in the x direction.
    • This means that the conservation law needs to hold in any frame of reference.

  • Relativistic Addition of Velocities

    • A velocity-addition formula is an equation that relates the velocities of moving objects in different reference frames.
    • A velocity-addition formula is an equation that relates the velocities of moving objects in different reference frames.
    • According to the theory of special relativity, the frame of the ship has a different clock rate and distance measure, and the notion of simultaneity in the direction of motion is altered, so the addition law for velocities is changed.
    • Since special relativity dictates that the speed of light is the same in all frames of reference, light shone from the front of a moving car can't go faster than light from a stationary lamp.
    • Composition law for velocities gave the first test of the kinematics of the special theory of relativity.

  • Length

    • Length is a measure of one dimension, whereas area is a measure of two dimensions (length squared) and volume is a measure of three dimensions (length cubed).
    • After Albert Einstein's Special Relativity Theory, length can no longer be thought of being constant in all reference frames.
    • Thus, a ruler that is one meter long in one frame of reference will not be one meter long in a reference frame that is travelling at a velocity relative to the first frame.
    • One of the oldest units of length measurement used in the ancient world was the 'cubit,' which was the length of the arm from the tip of the finger to the elbow.
    • Units of length may be based on lengths of human body parts, the distance traveled in a number of paces, the distance between landmarks or places on the Earth, or arbitrarily on the length of some fixed object.In the International System of Units (SI), the basic unit of length is the meter and is now defined in terms of the speed of light.

  • Gallilean-Newtonian Relativity

    • The fact that the Earth orbits around the sun at approximately 30 km/s offers a somewhat more dramatic example, though it is technically not an inertial reference frame.
    • Specifically, the term Galilean invariance today usually refers to this principle as applied to Newtonian mechanics—that is, Newton's laws hold in all inertial frames.
    • An inertial frame is a reference frame in relative uniform motion to absolute space.
    • This transformation of variables between two inertial frames is called Galilean transformation .
    • Assuming that mass is invariant in all inertial frames, the above equation shows that Newton's laws of mechanics, if valid in one frame, must hold for all frames.