The distance moved by an object in a unit time is called its speed. Speed is a scalar quantity that refers to “how fast an object is moving.” Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a short amount of time. A slow-moving object has a low speed and covers a relatively small amount of distance in a short amount of time. An object with no movement at all has a zero speed, the speed of an object is the magnitude of its velocity(the rate of change of its position) it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero .
Distance travelled per unit time. Speed is the scalar quantity that is the magnitude of the velocity vector. The most common way to calculate the constant velocity of an object moving in a straight line is with the formula:
(Speed =Total distance covered / Total time taken)
r = d / t
where
• r is the rate, or speed
• d is the distance moved
• t is the time it takes to complete the movement
The SI units for speed are m / s (meters per second).
If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform. On the other hand, an object moving along a straight line with a constant speed is said to be in uniform motion. In this case, the average speed is the same as the actual speed.