Measurement of Speed

Speed isn’t only about numbers; it’s a change in movement itself. Like other measurable quantity speed also has its advantages. So, join us on the journey to uncover the hidden art of measuring speed.

Further in this article, we will learn about the statement, formula, its dimensional formula, various types, measurement of speed, various instruments for measurement of speed, velocity, and difference between velocity and speed. Additionally, there will be a few practice problems for better understanding and clarification.

What is Speed?

Speed is a fundamental concept in physics, and is given by,

The rate of change of an object in any direction.

Speed is a scalar quantity; hence no direction only magnitude is present.

Speed Definition

Speed has only magnitude, its the rate of motion without any direction. It’s a scalar quantity. It is measured in units like meters per second (m/s) or kilometers per hour (km/h).

Speed Formula

The formula of speed is given by,

Speed = D/T

where,

• D is the Distance Traveled
• T is the Time Taken

Its units is given by,

• In CGS system cm.s^-1
• In SI system m.s^-1

Dimensional Formula of Speed

As we know spped is given by distance divided by time its dimensional formula is given as,

Dimensional Formula of Speed = [M⁰L¹T^-1]

Types of Speed

Different types of speed are:

• Uniform Speed
• Variable Speed
• Average Speed
• Instantaneous Speed
• Relative Speed

Let’s learn about them in brief.

Uniform Speed

Constant rate of motion without any change in velocity.

v_uniform = Total Distance/Total Time

For example: A car cruzing at 80 kmph on a highway.

Variable Speed

Motion of an object that changes pace or rate over time.

v_variable = Change in Distance/Change in Time

For example: A car moving from point A to B cruzing and taking multiple stops.

Average Speed

The total distance traveled divided by the total time taken.

v_avg = Total Distance/Total Time

For example, speed of car in moving form point A to B.

Instantaneous Speed

The speed of an object at a particular moment in time.

v = lim_Δt→0 Δd/Δt

For example, speed of accelerating car.

Relative Speed

The speed of an object observed from another moving object.

v_relative = v₁ ∓ v₂

(plus when moving in same direction, minus when moving in opposite direction)

For example, spped of car with respect to a moving bicyle.

What is Measurement of Speed?

Speed is rate of change of any object, not just movement. There are various speed measuring devices which calculate different aspect of speed for instance Speedometers measure vehicle speed, odometers track distance, and graphs illustrate motion. However, speed’s definition varies based on context.

For example, in melting ice, it’s the rate of transformation, not motion. Similarly, a ‘slow’ laptop refers to processing efficiency, not physical speed.

Measurement of Speed of Light

Speed of light, denoted by “c,” which is approximately 299,792,458 meter/second, it serves as the limit for energy, matter, and information transmission in space.

Ole Romer’s 1676 observations of Jupiter’s moon marked as the first indication of light speed. Then Albert Einstein’s 1905 theory of relativity made c as a universal constant.

Measurement of Speed of Sound

Sound’s speed, is the distance a sound wave travels per unit time. At 20℃, sound travels at around 343 meter/second in air. The speed varies with the medium, being slowest in gases, faster in liquids, and fastest in solids.

The speed of sound, plays a vital part in fields like meteorology, affecting weather forecasting and various applications.

Measurement of Speed of Wind

Wind speed measures the movement of air from low to high pressure zones. Anemometers, instruments designed for this purpose, which quantify wind speed. Wind speed impacts all the aspects of nature by affecting weather forecasting, aviation, maritime operations, and ultimately influencing plant biology. Understanding wind speed is very important for the advancement of applications and better prediction atmospheric conditions.

Measurement of Speed Instruments

Various instruments used to measure the spped are,

• Speedometer
• Tachometer
• Accelerometer

Speedometer: A speedometer is a device which measures the vehicle speed in kilometers per hour or miles per hour.

Tachometer: A tachometer is a device which measure the working speed of an engine in revolutions per minute(RPM).

Accelerometer: An accelerometer is a device which measure the acceleration of a moving body.

What is Velocity?

Velocity is defined as,

The rate at which an object’s position changes with respect to time in specific direction is called velocity

Velocity is a vector quantity hence both direction and magnitude is present.

Formula of velocity is given by,

Velocity = Change in Displacement/Change in Time

Difference between Speed and Velocity

The general differnce between speed and velocity is added in the table below as,

Speed Vs Velocity
Characteristic	Speed	Velocity
Definition	Distance traveled by an object over time.	Change in distance in a specific direction over time.
Quantity Type	Scalar quantity	Vector quantity
Example	60 km/hour	60 km/hour East
Real-life Scenario	Running on a treadmill at constant speed.	Driving a car with changes in speed and direction.

Conclusion

By understanding the speed of an object, from its definitions to various types, it become important in understanding the motion of objects. Whether knowing the instantaneous speed of an object or calculating the overall distance of a journey, speed helps us. And helps us in our understanding the concept of velocity and motion.

Read More,

• Escape Velocity
• Distance and Displacement 
• Acceleration
• Speed and Velocity

Examples Measurement of Speed

Some examples on measurement of speed are,

Example 1. A car travels a distance of 150 kilometers in 2.5 hours. Calculate its average speed.

Solution:

Average Speed =Total Distance/Total Time

Average Speed = 150 km / 2.5 hours

Average Speed = 60 km/hour

Example 2. An athlete runs a 100-meter race in 10 seconds. Determine the athlete’s speed.

Solution:

Speed = Time/Distance

Speed = 100 meters / 10 seconds

Speed = 10m/s

Example 3. A sprinter accelerates from rest to a speed of 8 m/s in 4 seconds. Calculate the sprinter’s acceleration.

Solution:

Acceleration = Change in Velocity / Time

Acceleration = (8 m/s − 0) / 4 s

Acceleration = 2m/s²

Measurement of Speed FAQs

What is Speed?

Its the ratio of the distance travelled in the given time.

How to Measure the Speed?

It can be measured by its formula,

Speed = Distance/Time

What Unit of Speed?

The unit of speed is m.s^-1

How is Speed Measured in Vehicles?

Speedometers in vehicles measure speed.