Constant vs Instantaneous Speed

Speed may be defined as the distance traveled per unit of time. There can be many instances of speed, such as constant speed, average speed, and instantaneous speed.

Constant Speed
A fixed distance movement per unit of time is constant speed. At each interval of time, the same amount of distance is covered. A suitable example of constant speed might be an object moving in an orbit. “Constant speed” means that over time the speed neither increases nor decreases; it just remains consistent. This means that velocity as well as acceleration is absent, or it is equal to zero. In other words, if speed is constant, there is no acceleration or velocity involved. Constant speed with a direction vector becomes velocity. Velocity changes constantly as its direction changes constantly. Constant speed is a scalar quantity.
If we divide the total distance traversed by the total time, we get the average speed. Thus,
Average speed=total distance/total time
S = d / t

Instantaneous Speed
The speed at a particular time is instantaneous speed. It can be taken from a point which lies on the line of a time-speed graph. Instantaneous speed is measured differently on a time-distance graph. At a certain point, the velocity of an object gives the instantaneous speed.

Suppose you are driving a car with your friend. If you observe the readings of the speedometer, its speed constantly changes because the speedometer gives the speed at a particular time. That reading is the instantaneous speed at that very instance. If at an instant in time the distance traversed is divided by the arbitrarily small traversal time, the instantaneous speed is obtained. It can be written as a derivative.

The instantaneous speed of an object can be calculated by using limits. Suppose one decides to drop a ball out of his second-floor window. There is a formula that tells how far it will fall after a given numbers of seconds (ignoring the air resistance).
S=16t2; where
“S” is distance the ball has fallen and
“t” is the time taken to travel the distance.
If we put the value of “t” as “1,” then the ball will fall 16 feet in the first second. So the average speed may be calculated as the distance divided by the time i.e. 16/1 = 16 ft/sec.
The instantaneous speed of an object can also be determined through calculating the average speed over a short distance and time.

Summary:

“Constant speed” means an object is moving at the same speed throughout. In daily life, it can be said that the faster object has a faster speed. Constant speed neither increases nor decreases over time but remains constant. Earth revolves at a constant speed around the sun in a certain orbit. Satellites also revolve at constant speeds in a certain path. Instantaneous speed is a certain speed at a specific instant in time. At a certain instant, what the speedometer reads is the instantaneous speed.

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