Speed and average speed In this section you will:- be able to work out the average speed of a journey be able to recognise different speeds by looking at distance-time graphs.

. __ Speed = distance time To work out the speed something is travelling with We need to measure 2 things: the distance the object has travelled the time it takes for the journey __ . Speed = distance time (in metres per second or m/s) (in metres) (in seconds)

. . . __ Speed = distance time Average = total distance total time (in metres per second or m/s) (in metres) (in seconds) . Average = total distance total time Speed travelled taken .

. . Bald Bob goes on a journey Stage 1 = 5m in ___s 2 Bald Bob goes on a journey Stage 1 5metres 2 0m Stage 3 31metres Average speed = total distance/total time taken Use this equation to work out the average speed of Bobs journey . . Average speed = Answer =

Bald Bob goes on a journey Stage 1 = 5m in ___s Stage 2 = 0m in ___s Stage 3 = 31m in ___s 5 Speed is _____m/s 1 slowest 5 15.5 fastest 2 Bald Bob goes on a journey Stage 1 5metres 2 0m Stage 3 31metres Average speed = total distance/total time taken 36 /12 =3m/s

The steeper the graph the faster the object distance distance distance Stationary (stopped) fast slow time time time Slow car Fast car Stopped car The steeper the graph the faster the object is moving. A horizontal line is a stationary object

Work out the average speeds of the following 4 journeys

. . Bald Bob Average speed = Answer = Distance/m 300 fastest slowest 12 Time/s

. . Mum Average speed = Distance/m Answer = 20 15 10 fastest 5 slowest fastest slowest 5 10 15 20 25 30 35 40 45 50 55 60 65 Time/s

. . . . . . Snooty Sarah Answer = Distance /m Answer = 30 slowest 20 Fastest speed = Answer = . . Distance /m speed in the final stage= Answer = 30 slowest 20 fastest . 10 . 40 60 Time/s Average speed = Answer =

. . Dippy Daisy Average speed = Answer = Distance/m 30 slowest fastest 20 Time/s

Answers:- Bald Bob 300/12 = 25m/s Mum 20/50 = 0.4m/s Snooty Sarah fastest =20/10 = 2m/s final stage = 10/20 = 0.5m/s average speed = 30/60=0.5m/s Dippy Daisy average speed = 60/20 = 3m/s

Speed is worked out by dividing the distance by the An object travels 15metres in 5seconds so it’s speed will be The average speed is worked out by dividing the total distance by the The average speed of an object going 10m in 6s and 20m in 4s is An object that is not moving will produce a distance-time graph that is Objects moving with a steady fast speed will make a line that is Objects moving with a steady slow speed will make a line that is The distance an object travels is measured in The time an object takes to travel is measured in The speed of an object is measured in A steep line would be made by an object moving A flat line would be made by a person who is A line with a small slope would be made by an object moving An object which speeds up is said to be An object which slows down is said to be

Time 3m/s Total time 30/10=3m/s Horizontal Steep Shallow(not very steep) Metres or kilometres Seconds or hours km/h or m/s Quickly Stationary Slowly Accelerating decelerating Speed is worked out by dividing the distance by the An object travels 15metres in 5seconds so it’s speed will be The average speed is worked out by dividing the total distance by the The average speed of an object going 10m in 6s and 20m in 4s is An object that is not moving will produce a distance-time graph that is Objects moving with a steady fast speed will make a line that is Objects moving with a steady slow speed will make a line that is The distance an object travels is measured in The time an object takes to travel is measured in The speed of an object is measured in A steep line would be made by an object moving A flat line would be made by a person A line with a small slope would be made by an object moving An object which speeds up is said to be An object which slows down is said to be

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