Speed

In the image below, the athlete will cover a certain distance in a certain time.

This is called Speed.

#### Example

The speed of these cars is over 150 kilometers per hour (150 km/h).

#### Speed

Speed is how fast something is moving

Speed is a measure of the distance travelled in a given time.

Distance is measured in Metres and Kilometres as the distance travelled per unit of time.

Time is measured Seconds, Minutes and  Hours

#### Example

An athlete runs around a circular track on a field of diameter 336 m in 5 minutes. She adjusts her shoes for 30 seconds then covers the second lap in 6 minutes.

Calculate

(a) her speed in km/h during the first lap.

(b) her average speed for the whole time interval (take π = 22/7)

## Distance = 2`Pir`

`= 2 x 22/7 x 336/2`

`= 1056 meters`

`1 Km = 1000 M`

`1056/1000 Km`

`=1.056 Km`

` `

`Time:`

5 `1/2 mins`

`=` 5`1/2` ` ``-:60`

`=11/120hrs`

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#### Speed

= `1056/1000 x 120/11`

`=115.2Km/h`

`(2 x 1056m ) for 2 trips`

`= 2 x 1056/1000Km`

`=1.056x2`

Time

= 5 `1/2 mins + 1/2 mins + 6 mins`

= 12 mins

`12/60 hrs`

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