Editing Speed (section)

=== Historical definition ===
Italian physicist [[Galileo Galilei]] is usually credited with being the first to measure speed by considering the distance covered and the time it takes. Galileo defined speed as the distance covered per unit of time.<ref name="Hewitt 2007, p. 42">{{harvnb|Hewitt|2007|p=42}}</ref> In equation form, that is
<math display=block qid=Q3711325 id=main_formula>v = \frac{d}{t},</math>
where <math>v</math> is speed, <math>d</math> is distance, and <math>t</math> is time. A cyclist who covers 30 metres in a time of 2 seconds, for example, has a speed of 15 metres per second. Objects in motion often have variations in speed (a car might travel along a street at 50&nbsp;km/h, slow to 0&nbsp;km/h, and then reach 30&nbsp;km/h).