أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ٥_ s

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 5_ S


speed(c)
vitesse f

Speed. The rate of change of distance, its unit is meters per second (m/s), and speed is a scalar measurement since direction is not important. Thus, the maximum speed of a car, for example, does not depend on the direction in which it is traveling. As for the (linear) velocity. On the other hand, it is a vector.

Speed ​​l/t = c. Speed ​​s/t = v.


speed of light
Vitesse f de la lumière

The speed of light. Relativity says that no object can accelerate to the speed of light in empty space, that is, 300,000 km/s. Electromagnetic waves travel at this speed in space, but inside matter they move at much slower speeds that depend on the material and the wavelength. See refractive index

The speed of light was first known by observing how the observed eclipses of Jupiter's moons depend on the planet's distance from Earth. Modern methods use very precise timings over short distances.


speed of sound
Vitesse f du son

The speed of sound. The speed, c, of sound and other pressure waves through matter depends on the elasticity and density of the medium. Although the densities of solids and liquids are much greater than those of gases, their elasticity is also much higher. As a result, the speed of sound in gases is slower. The data in the following table are traditional data:

Medium ---- speed m/s

Air ------- 300
Water ------- 1500
Steel ------- 6000

The speed of sound in a given substance increases as the temperature increases. If the frequency is also high, it depends on it as well.

We can measure the speed of sound either by timing the reflection of a short sound pulse (compare with sonar), or by creating standing waves in a sample.

Objects moving in the air at a speed greater than the speed of sound have supersonic speed. Shock waves are formed around these objects, causing the sonic boom known as the Concorde plane to explode and the sound of a long whip to crack.


stability
stability f

Stability. This term describes how difficult it is to upset an object's equilibrium. A body is stable if a disturbance generates a force that returns the body to its original position. The black objects in the figure below are very stable.

If the force restoring stability is gravity (earthly gravity), then we often talk about stability (a) below, instability (b) and neutrality (c) in equilibrium.

The disturbance raises the center of mass in (a) and lowers it in (b) and does not change its level in (c). The body tends to return to its original position (A), move away from it (B), or remain in its new state (C).


standard form
form f standard

Standard format. It is often best to express numbers in the form 1.25 x 102, where the decimal point follows the first digit. Thus, the numbers in standard form range from 1.00×10n to 9.99×10n. The use of this method to express numbers is detailed when dealing with very large numbers, such as the speed of light.