Average Speed vs Instantaneous Speed

Kinematics is the science, or field of study, concerning the motion of objects. It is without the consideration of the causes of movement, and this specific branch of science extensively involves speed and velocity.

People have been always fascinated with speed. It has been pondered for centuries by analytical minds, and has become one of the major subjects of competitions – such as foot races, swimming, horse races, chariot races, car races, and other vehicular races.

Speed is the scalar equivalent of velocity, and in physics and engineering, there are many ways of expressing or describing it, which in turn can become very confusing for many people to comprehend.

In this article, we tackle two of the more confusing ways to express the rate of motion ‘“ average speed and instantaneous speed.

The most commonly known device or equipment that describes speed, is the speedometer. Speedometers are staple components of almost all moving/transportation vehicles. The information revealed by the equipment is instantaneous speed.

As you may have already noticed, the readings on the speedometer constantly changes as you use your car in your travels ‘“ for instance, your trip from home to work. In a dense highway, the traffic is slow, and you may go as slow as 15 km/h, which will be what the speedometer shows. Conversely, on a freeway you could go as fast as 100 km/h, or faster. At different moments, you have different speeds.

Having said all of that, instantaneous speed is defined as the speed at any given moment in time. It is practically what our car’s speedometer displays – your 15 km/h speed in the moment of dense traffic, and 100 km/h on freeways.

Average speed, on the other hand, is describing your rate of motion as a whole. Using the same analogy above, the average speed is the description of the rate of travel for your whole course -i.e. from your home to work. It includes the moments of heavy traffic and the frantic pace of the freeway. Assuming that the whole distance traveled is 40 km, and you made it in just one hour, your average speed will then be 40 km/h.

Thus, average speed is defined as the overall rate at which an object moves. Mathematically:

Average speed = (Overall Travel Distance) / (Time Elapsed to cover that distance)

In theory, when you calculate the average of all instantaneous speeds that occurred during the whole trip, you will get the average speed.

Summary:

1. Instantaneous speed and average speed are both scalar quantities.

2. Instantaneous speed is the speed at any given instant in time.

3. Average speed is the overall rate at which an object moves.

4. The speedometer describes instantaneous speed.

5. When you solve the average of all instantaneous speeds that occurred during the whole trip, you will get the average speed.

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