If you haven't dealt with calculus, don't sweat this definition too much. Or, in the language of calculus speed is the first derivative of distance with respect to time. This idea is written symbolically as… v = Mentally, however, it is possible to imagine calculating average speed over ever smaller time intervals until we have effectively calculated instantaneous speed. Ideally this interval should be as close to zero as possible, but in reality we are limited by the sensitivity of our measuring devices. In contrast, a car's speedometer shows its instantaneous speed, that is, the speed determined over a very small interval of time - an instant. This is the quantity we calculated for our hypothetical trip. Read it as 'vee bar is delta ess over delta tee'. The bar over the v indicates an average or a mean and the ∆ (delta) symbol indicates a change. In order to emphasize this point, the equation is sometimes modified as follows… v = Thus, the number calculated above is not the speed of the car, it's the average speed for the entire journey. Unless you live in a world where cars have some kind of exceptional cruise control and traffic flows in some ideal manner, your speed during this hypothetical journey must certainly have varied. This is the answer the equation gives us, but how right is it? Was 75 kph the speed of the car? Yes, of course it was… Well, maybe, I guess… No, it couldn't have been the speed. If the trip takes four hours, what was your speed? Applying the formula above gives… v = The distance by road is roughly 300 km (200 miles). Let's say you drove a car from New York to Boston. 'Farther' and 'sooner' correspond to 'faster'. In order to calculate the speed of an object we must know how far it's gone and how long it took to get there. Speed is the rate of change of distance with time. v =ĭon't like symbols? Well then, here's another way to define speed. Speed is inversely proportional to time when distance is constant: v ∝ 1 t ( s constant)Ĭombining these two rules together gives the definition of speed in symbolic form.

Speed is directly proportional to distance when time is constant: v ∝ s ( t constant).

(The symbol v is used for speed because of the association between speed and velocity, which will be discussed shortly.)

If you know a little about mathematics, these statements are meaningful and useful. Doubling one's speed would also mean halving the time required to travel a given distance. 'Faster' means either 'farther' (greater distance) or 'sooner' (less time).ĭoubling one's speed would mean doubling one's distance traveled in a given amount of time.

Whatever speed is, it involves both distance and time. Either that or they'll tell you that the one moving faster will get where it's going sooner than the slower one. Speed of sound conversions: a compehensive list with conversions from speed of sound to other (metric, imperial, or customary) speed and velocity measurement units is presented below.What's the difference between two identical objects traveling at different speeds? Nearly everyone knows that the one moving faster (the one with the greater speed) will go farther than the one moving slower in the same amount of time. The speed sound travels through iron at 20 ☌ is about 5,120 m/s (i.e., about 15 times faster than in dry air at the same temperature).The speed sound travels through water at 20 ☌ (68 ☏) is about 1,484 m/s (i.e., nearly 4.3 times faster than in dry air at the same temperature).Specifically, the sound wave travels faster in liquids and non-porous solids than it does in air: The speed of sound varies depending on the medium the sound wave travels. The speed of sound is also equal to approximately 1,236 kilometers per hour ( km/h), or 1,126 feet per second ( ft/s), or 768 miles per hour ( mph), or approximately one mile in five seconds or about one kilometer in three seconds. In dry air at 20 ☌ (68 ☏), the speed of sound is equal to 343.2 meters per second ( m/s), the derived unit of speed in the International System of Units ( SI). The speed of sound is the distance traveled by a sound wave through an elastic medium during a period of time. To make a conversion starting from a unit of speed other than speed of sound, simply click on the 'Reset' button. The speed of sound conversion selector selects the speed/velocity measurement unit to convert to starting from speed of sound.

Whats the speed of sound in mph