**What is Speed?**

Speed tells how fast you are covering distance in a particular time.

Given above are the image of two cars.

Speed of Car A = 50 km/hr

It tells that car A travels 50 km distance in 1 hour time

Speed of Car B = 120 km/hr

It means car B travels 120 km distance in 1 hour

Hence, Speed of Car A > Car B as it travels more distance in one hour time

**Formula for Speed**

The speed of any object can be calculated using following formula

** \mathtt{Speed=\frac{Distance}{Time}} \\\ \\ \mathtt{S\ =\ \frac{D}{T}} **

Hence, if you know the distance covered by object at a particular time, you can calculate its speed.

**Example 01**

A car travels 60 km distance in 3 hours. Find the speed of the car

Given

Distance travelled (D) = 60 Km

Time taken (T) = 3 hours

\mathtt{Speed=\frac{Distance}{Time} \ }\\\ \\ \mathtt{Speed\ =\ \frac{60}{3} \ =\ 20\ km/hr}

Hence, the speed of car is 20 km/hr**It also means that the car travels 20 km in one hour**

**Example 02**A scooter travels 20 meter in 5 seconds. Find the speed

Given

Distance Travelled (D) = 20 meter

Time taken (T) = 5 seconds

\mathtt{Speed=\frac{Distance}{Time} \ }\\\ \\ \mathtt{Speed\ =\ \frac{20}{5} \ =\ 4\ m/sec}

Hence, the speed of scooter is 4 meter/second**It also means that scooter travels 4 meter every one second**

**Unit of Speed**

The standard unit of speed is **meter/seconds**

Other common units for expressing speed are:

⟹ kilometer/hour (km/hr)

⟹ miles/hour (mph)

⟹ meter/second (m/s)

**Explanation**

The below cyclist covers 27 meter distance in 9 seconds.

Find the speed

We know that;

\mathtt{Speed=\frac{Distance}{Time} \ }\\\ \\ \mathtt{Speed\ =\ \frac{27\ meter}{9\ seconds} \ =\ 3\ m/sec}

**Observe how speed is expressed in meter/seconds (m/s) after the formula calculation**

**Converting meter/second to kilometer**

Some questions specifically ask about speed converted in km/hr.

Below is the shortcut to convert speed from m/s to km/hr

we know that:

1 meter = 0.001 Km

1 hour = 60 x 60 seconds = 3600 seconds

1 second = 1/3600 hour

Converting meter/second into km/hr

\mathtt{\frac{meter}{second} \ =\ \frac{0.001\ km}{\frac{1}{3600} \ hr} \ =\ 3.6\ km/hr}

**Conclusion: To convert speed from meter/sec to Km/hr just multiply the speed with 3.6**

**How to calculate Distance Travelled**

When you know the speed of the object and the time of travel, you can easily calculate the distance using the speed formula mentioned above

We know that:

\mathtt{Speed\ =\ \frac{Distance}{Time}}\\\ \\ \mathtt{Distance\ =\ Speed\ \times \ Time}

**Speed, Distance, Time – Questions**

**(01) A car travelled at the speed of 30 km/hr for 10 minutes. Find the distance travelled by the car**

Given

Speed (S) = 30 km/hr

Time (T) = 10 minutes

Here the speed is given in km/hr, while time is in minutes.

To make data consistent, convert the time into hour

we know that

1 minute = 1/60 Hour

10 minute = 1/6 Hour

Now the time (T) is = 1/6 Hour

Using the formula:**Distance = Speed x Time**

Distance = 30 x (1/6) = 5 km

**Hence, the distance travelled by car is 5 Km**

**(02) Distance between city A & city B is 20,000 meter. A car travels from A to B in 45 minutes. Find the speed of the car in km/hr.**

Given

Distance = 20,000 meter

we know that;

1 meter = 0.001 Km

20,000 meter = 20,000 x 0.001 = 20 Km

Time taken = 45 minutes

we know that;

1 minute = 1/60 hour

45 minute = 45/60 hour = 3/4 Hour

Hence,

Distance (D) = 20 Km

Time (T)= 3/4 Hour

We know that;**Speed = Distance/Time**

\mathtt{Speed\ =\ \frac{20}{\frac{3}{4}}}\\\ \\ \mathtt{Speed\ \ =\ \frac{20\times 4}{3} \ =\frac{80}{3} \ =\ 26.7\ Km/hr}

**Hence, the speed of car is 26.7 km/hr**

**(03) A bird flies at the speed for 3 hours at the speed of 15 km/hr. Find the distance travelled by bird in meter**

Solution

Speed (S) = 15 Km/hr

Time (T) = 3 hours

Using the formula;

Distance\ =\ Speed\ \times \ Time\\\ \\ Distance\ =\ 15\ \times \ 3\ =\ 45\ km

We have to calculate distance in meters.

we know that;

1 km = 1000 meter

45 km = 45,000 meter

**Hence, 45000 meter is the solution**

**(04) A spacecraft travels at the speed of 15 km/second. Find the distance travelled in 2 hours.**

Speed = 15 km/sec

Convert km/sec into km/hr

We know that;

1 second = (1/3600) hour

\mathtt{\Longrightarrow \ 15\ \ \frac{km\ }{sec} \ }\\\ \\ \mathtt{\Longrightarrow \ 15\ \frac{km}{\frac{hr}{3600}} \ }\\\ \\ \mathtt{\Longrightarrow \ 54000\ \frac{km}{hr} \ }

Hence;

Speed (S) = 54000 km/hr

Time (T) = 2 hr

Using the formula;**Distance = Speed x Time**

Distance = 54000 x 2 = 108000 kms

**Hence, the space craft will travel 108000kms in 2 hours**