We use the word speed in our life every day. We actually use velocity and speed interchangeably. But they are completely different. So, today we are going to learn what is speed, the definition and speed formula, and understand how speed is calculated with various examples. Are you ready to learn everything about speed? Let us begin…

What is Speed?

Speed is a measurement of how quickly an object can move from one place to another.

Speed is a scalar quantity meaning it has a magnitude but has no direction.

Definition of Speed

Galileo was considered to have given the definition of speed. Speed is defined as the distance covered per unit time.

The speed formula is given below:

Speed = Distance/Time

With this formula you can find out distance and time as well.

For distance, the formula is:

Distance = Speed * Time

For time, the formula is:

Time = Distance/Speed

The units of measurement for speed are:

  • Meters per second or m/s. It is the most used unit of measurement of speed.
  • Miles per hour or mph
  • Kilometers per hour or kmph
  • Feet per second or fps
  • Nautical miles per hour called Knots or kn or kt (This is used in oceans and seas)

The unit of measurement of distance is meters/kilometers/miles/feet.

The unit of measurement of time is seconds or hours.

Types of Speed

There are four types of speed which are briefly described below.

Uniform Speed – When the object covers equal distance in equal time intervals, it is said to have uniform speed.

Example: Movement of fan, Earth moving around the Sun, the hour hand of clocks. In all three examples, the object (fan, Earth, and hour hand move at a uniform or steady speed).

Average Speed – The total distance covered by an object in a given time is called average speed.

Example: If X walked 10 kilometers in 2 hours, then his average speed is: 10/2 = 5 kilometers per hour.

Variable Speed – When the object covers different distances in equal time intervals, it is said to have variable speed.

Example: Horse running, a bus on a busy road, and a train reaching its terminal point. In all three examples, the object (horse, bus, train move at different speeds).

Instantaneous Speed – The speed of an object at that very instant is called instantaneous speed.

Example: Speedometer of a car shows instantaneous speed.

Examples of Speed and Speed Formula Usage

1. A man walks 21 miles in 3 hours. Calculate his speed using the speed formula


Distance is 21 miles and time is 3 hours, so using the formula of speed, we get –

Speed = Distance/Time

S = 21/3

S = 7 miles per hour or mph.

2. A car moves at a speed of 50 miles per hour. How much time will the car take to cover a total distance of 150 miles?


Distance = 150 miles

Speed = 50 miles per hour

Time = Distance/Speed

T = 150/50

T = 3 hours.

The car would take three hours to cover a distance of 150 miles.

3. A dog ran at a speed of 15 miles per hour for 3 hours. What is the total distance the dog ran?


Speed = 15 miles per hour

Time taken = 3 hours

Distance = Speed * Time

D = 15 * 3

D = 45 miles

The dog ran a total distance of 45 miles in three hours at a speed of 15 miles per hour.

4. What is 360 kilometers per hour in meters per second?


Speed = 360 kmph

Tip: 1 meter per second = 3.6 kilometers per hour

1 kmph = 1 (m/s)/3.6 (km/h)

With this tip we can easily convert the speed from kmph to m/s.

360 * 1/3.6 = 100 m/s

5. A boy traveled in a car at a speed of 45 mph. The entire distance was 120 miles. How much time did it take to reach the destination?


Speed = 45 mph

Distance = 120 miles

Time = Distance/speed

T = 120/45

T = 2.66 hours

The boy would take 2.66 hours to reach the destination.

6. A man traveled a distance of 200 kilometers. The journey lasted for four hours. What was the speed of the man?


Distance = 200 kilometers

Time = 4 hours

Speed = Distance/Time

S = 200/4

S = 50 kmph

The man travelled a distance of 200 kilometers at a speed of 50 kmph for 4 hours.

7. A cat ran for 3 hours at a speed of 15 kilometers per hour. What is the distance traveled by cat?


Speed = 15 kilometers per hour

Time = 3 hours

Distance = Speed * Time

Distance = 15 * 3

Distance = 45 kilometers.

The cat traveled a distance of 45 kilometers in three hours maintaining a speed of 15 kilometers per hour.

8. What is 250 meters per second in kilometers per hour?


Speed in meters per second = 250

1 meter per second = 3.6 kilometers per hour

250 * 3.6 = 900 kilometers per hour

9. A girl traveled from A to B in 6 hours at a speed of 54 miles per hour. What is the total distance covered?


Time = 9 hours

Speed = 54 miles per hour

Distance = Speed * Time

Distance = 54 * 9

Distance = 486 miles

The girl traveled for a total distance of 486 miles in six hours maintaining a speed of 54 miles per hour.

10. A train travels from Baltimore to Washington and comes back to its original position in 1.5 hours. The distance covered is 40 miles. What is the speed of the train?


Time = 1.5 hours

Distance = 40 * 2 = 80 (because train traveled back and forth)

Speed = Distance/Time

Speed = 80/1.5

Speed = 53.33 miles per hour

Train traveled 53.33 miles per hour to cover a distance of 80 miles for 1.5 hours.

So, did you like the explanation of speed and speed formula? If you want us to create some questions for you to solve, then please drop a comment in the comment box.

While you can always calculate speed by yourself, if you need to use an online calculator, here is one for you.

Sources: BBC, MathisFun

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