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  2. Speed of sound - Wikipedia

    en.wikipedia.org/wiki/Speed_of_sound

    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.

  3. Speed - Wikipedia

    en.wikipedia.org/wiki/Speed

    L T−1. In kinematics, the speed (commonly referred to as v) of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. [1] The average speed of an object in an interval of time is the distance travelled by the object divided ...

  4. Naismith's rule - Wikipedia

    en.wikipedia.org/wiki/Naismith's_rule

    Assuming an individual can maintain a speed on the flat of 5 km/h, the route will take 6 hours and 34 minutes. The simplicity of this approach is that the time taken can be easily adjusted for an individual's own (chosen) speed on the flat; at 8 km/h (flat speed) the route will take 4 hours and 6 minutes.

  5. Wind gradient - Wikipedia

    en.wikipedia.org/wiki/Wind_gradient

    Wind gradient. In common usage, wind gradient, more specifically wind speed gradient[1] or wind velocity gradient, [2] or alternatively shear wind, [3] is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. [4] It is the rate of increase of wind strength with unit increase in height above ground ...

  6. Spacetime diagram - Wikipedia

    en.wikipedia.org/wiki/Spacetime_diagram

    A spacetime diagram is a graphical illustration of locations in space at various times, especially in the special theory of relativity. Spacetime diagrams can show the geometry underlying phenomena like time dilation and length contraction without mathematical equations. The history of an object's location through time traces out a line or ...

  7. Motion graphs and derivatives - Wikipedia

    en.wikipedia.org/wiki/Motion_graphs_and_derivatives

    Motion graphs and derivatives. The green line shows the slope of the velocity-time graph at the particular point where the two lines touch. Its slope is the acceleration at that point. In mechanics, the derivative of the position vs. time graph of an object is equal to the velocity of the object. In the International System of Units, the ...

  8. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    It is described by the equation v = H 0 D, with H 0 the constant of proportionality—the Hubble constant—between the "proper distance" D to a galaxy (which can change over time, unlike the comoving distance) and its speed of separation v, i.e. the derivative of proper distance with respect to the cosmic time coordinate.

  9. Pulse-Doppler radar - Wikipedia

    en.wikipedia.org/wiki/Pulse-Doppler_radar

    Pulse-Doppler systems measure the range to objects by measuring the elapsed time between sending a pulse of radio energy and receiving a reflection of the object. Radio waves travel at the speed of light, so the distance to the object is the elapsed time multiplied by the speed of light, divided by two – there and back.