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Measurement of Speed - Definition, Formula, Unit, Types, FAQs

Measurement of Speed - Definition, Formula, Unit, Types, FAQs

Edited By Team Careers360 | Updated on Jun 08, 2022 03:26 PM IST


The rate at which any body moves or operates with respect to time is called the speed of the body. In physics, the measurement of speed refers to the rate of change of position of a body with respect to time. The measurement of speed meaning may vary according to the condition it is applied to, for example in the case of a computer its measurement of speed do not usually indicate its motion but the processing speed of the processor, how much data can the processor handle in unit time and how fast it manages the assigned tasks, the computer speed is measured in Kb/s or KB/s. In the case of a motor, the rotation of the rotor is indicated in terms of RPM that is rotations per minute. Here we are going to see what is the speed in science

Measurement of speed in the computer is measured in terms of Kilobyte per second (KBps)

Distance and displacement

Distance refers to the measure of the entire route travelled by an object and it is a scalar quantity, distance is the measurement that is used to measure the speed of an object. Whereas the term displacement indicates the shortest route between the initial and the final positions of the body. The term displacement is a vector quantity and the displacement of a body is used to calculate the velocity of the body which is the rate of change of displacement with respect to time. The distance can only be a positive value or it has to be zero whereas the displacement of a body can be positive negative or zero. In the case of displacement, magnitude and direction is important as it is vector quantity.

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What is the Measurement of speed and velocity?

Measurement of speed is the rate of change of distance to time whereas the velocity of a body indicates the rate of change of displacement to time. That is the velocity has two parts one indicating a measure or the magnitude and the other indicating the direction of the velocity, it is not necessary that both these magnitude and direction components of velocity should remain the same always, change in any of these with respect to the time is called as the acceleration of the body.

What Measurement of speed in physics?

Speed meaning in physics is defined as how much distance a body covers in unit interval of time, if it is said that a body A has a higher measurement of speed than a body B then it indicates that the body A covers more distance than the body B in the same interval of time. suppose body A has a speed of 20 Km/hr and body B has 10km/hr . If they are able to maintain the measurement of speed constant through a journey of half an hour then body A has covered a distance of 10kms whereas Body B has covered only a distance of 5kms. The SI unit of speed or speed is measured in meters per second (m/s) but speed measurement in daily life is done in Kilometer per hour (Km/s) or miles per hour (mph) is used. We will see how to measure speed on the following sections

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What is the formula for speed?

when plotting a curve of distance covered by a body vs time, the slope of the graph gives the speed, different types of speed are normally instantaneous speed or average speed, speed formula is

Speed = distance/time

graph of retardation

graph of retardation

a body is said to be in unit speed if it covers 1 meter distance in 1 second and its formula is called unit speed formula

Speed = distance/time = 1m/1s = 1m/s

Average speed

Average speed can be defined as the total distance covered divided by the total time taken. For example, consider a body that covers a total of 200 km in varying speeds accelerating and decelerating at various rates in 5 hours which is what really happens in a road, there we make use of the term called the average speed which is the total distance covered in total time. The speed formula applied here is

Therefore, average speed = 200/5 = 40/1

Ie, average speed = 4 km per hour

Here speed is measured in km/hr for the better convenience

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Instantaneous speed

It is the measure of speed of a body at any instant of time, or measuring the rate of change of position with respect to an infinitesimally small time period. Consider a graph plotting distance of a body vs time then instantaneous speed is the derivative at any instant of time. Speed formula here is written as

Instantaneous speed = dr/dt

there is a usual convention that when talking about the velocity in physics, its magnitude part alone is usually called as speed as it is the part without direction but it may not conceptually agree because speed is a measure of total distance covered by the body and velocity is the shortest distance covered by the body, we know that distance may not be always equal to the displacement.

Uniform motion or uniform speed

Uniform speed indicates a case of motion of an object where rate of change of position to time is a constant throughout motion, in which the object covers equal distance in equal interval of time. In Non-uniform motion distance travelled by an object is not constantly measured in the same intervals of time.

When considering the graph it will be a straight line with constant slope, that is if we take the slope of the graph between any two points on the graph, it will remain the same always.(we have seen what the slope in a distance vs time graph indicates , it indicates the speed)

Uniform motion graph

Uniform motion graph (source self-made MS paint)

NCERT Physics Notes:

Non uniform motion

An object is said to be in non-uniform motion when there is an acceleration on the body that is the speed not always remains the same throughout the motion, it may increase or decrease accordingly.

The rate of increase or decrease of velocity with respect to time is called acceleration, above we have talked about uniform and non-uniform speed similarly there can be uniform or non-uniform acceleration also. Acceleration is a vector quantity so it cannot be mentioned in terms of speed but the magnitude of acceleration can be the rate of change of speed.

Graph of non-uniform motion

Graph of non-uniform motion

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Frequently Asked Question (FAQs)

1. What is speed or what is speed in physics or define speed in physics or speed definition physics or what is definition of speed and its speed formula ? or what is the formula for speed ?

Speedo meaning is rate of change of position to time and speed is a scalar quantity, it contains only magnitude and does not contain direction. Formula for speed is Speed = distance/time

2. What is variable speed? or define variable speed.

If a body undergoes any kind of acceleration, then the body is said to have variable speed, that is the speed is not constant at equal intervals of time.

3. Provide the example of speed.

The example of speed or application of speed is

  1. Speed of the vehicle

  2. Speed of rotation of the fan

  3. Speed of revolution of planets around sun

4. Optimum speed meaning in case of a rotor of a water pump.

It means the required number of rotations per unit time such that enough water is pumped into the surface, more rotation implies more water gets pumped.

5. What are the characteristics of speed?

Speed is the measure of motion and it can directly imply the amount of kinetic energy possessed by the body. If a body is said to have more speed than that of the other then it implies it can cover a much higher distance in less time.

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