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The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air, is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or 1 km in 2.91 s or one mile in 4.69 s.
[5] [3] [6] It explains simply and quantitatively why a body subject to a constant acceleration cannot reach the speed of light, and why the mass of a system emitting a photon decreases. [3] In relativistic quantum chemistry, relativistic mass is used to explain electron orbital contraction in heavy elements.
Acoustic theory is a scientific field that relates to the description of sound waves.It derives from fluid dynamics.See acoustics for the engineering approach.. For sound waves of any magnitude of a disturbance in velocity, pressure, and density we have
Therefore, the Newtonian definition of mass as the ratio of three-force and three-acceleration is disadvantageous in SR, because such a mass would depend both on velocity and direction. Consequently, the following mass definitions used in older textbooks are not used anymore: [ 27 ] [ 28 ] [ H 2 ]
Mass–energy equivalence states that all objects having mass, or massive objects, have a corresponding intrinsic energy, even when they are stationary.In the rest frame of an object, where by definition it is motionless and so has no momentum, the mass and energy are equal or they differ only by a constant factor, the speed of light squared (c 2).
where is the Laplace operator, is the acoustic pressure (the local deviation from the ambient pressure), and is the speed of sound. A similar looking wave equation but for the vector field particle velocity is given by
Each propagates at generally different speeds determined by the important function called the dispersion relation. The use of the explicit form ω ( k ) is standard, since the phase velocity ω / k and the group velocity d ω /d k usually have convenient representations by this function.
Terminal velocity (An object dropped through air from a sufficient height will reach a steady speed, called the terminal velocity, when the aerodynamic drag force pushing up on the body balances the gravitational force (weight) pulling the body down.) Nordtvedt effect; Newton's second law; Law of Inertia