Speed converter

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Speed in physics is a fundamental concept describing the distance an object travels per unit of time, indicating how fast an object moves.
Commonly, "speed" and "velocity" are used interchangeably in everyday language, yet they differ in physics: speed is a scalar (magnitude only) measured by distance over time, while velocity is a vector (magnitude and direction) measured by displacement over time. The SI unit for speed is meters per second (m/s), but kilometers per hour (km/h) or miles per hour (mph) are also used.
According to special relativity, the maximum speed at which energy or information can travel is the speed of light in a vacuum, approximately 299,792,458 meters per second.

In mathematical language, the average speed (denoted as $\overline{�}$) of an object moving a distance $�$ over a period $�$ is the ratio of $�$ to $�$, given by the formula:：

For example, if a car travels 60 kilometers in 2 hours, its average speed during this time is 30 kilometers per hour. The rate of an object at a specific moment is determined by the ratio of the distance 與traveled in a very short time ${\displaystyle dt}$ around that moment.：
To precisely define it, if the distance $�$ is a function of time $�$, then the instantaneous speed at a moment ${\displaystyle t_{0}}$ is the limit of the above ratio as ${\displaystyle dt}$ approaches zero, which mathematically means it's the derivative of ${\displaystyle s}$ with respect to$\mathrm{<br\; class="Apple-interchange-newline">\; �}$ at ${\displaystyle t_{0}}$.

In some simplified physical models, the rate of an object before a specific moment ${\displaystyle v_{t_{0}}^{-}}$may not equal its rate after that moment ${\displaystyle v_{t_{0}}^{+}}$：
For instance, in simple collision models, the velocity before and after the impact differs, highlighting discontinuities in rate changes that classical physics, which assumes continuous motion, doesn't account for. Instantaneous rate equals the magnitude of instantaneous speed, but average rate often doesn't equal average speed due to the distinction between path and displacement. For example, in uniform circular motion, the average rate is nonzero, but average speed is zero, illustrating the nuances in defining motion parameters. 

Units for measuring speed include: