Compound Measures OCR Stage 6

Speed - Distance - Time Part 1

What is speed? How far you travel in a certain time Speed = Distance ÷ Time We call the result “the average speed”

SDT Triangle You have seen this in Science? s d t x

d s t x = d = s x t = d ÷ s t Speed? Time? Distance? We can use this to find any one thing IF we know the other two! s d t x By covering up what you want Speed? Time? = d t = s x t Distance? = d ÷ s

A train travels 120 miles in 2 hours What is its average speed? mph s d t x MUST give UNITS MILES per HOUR

d s t x =s x t d = 8 x 25 Distance d = 200 metres A runner’s average speed is 8m/s, how far does he run in 25 seconds ? d = 8 x 25 Distance =s x t d = 200 metres s d t x MUST give UNITS Because speed was in METRES per second

Because speed was in km per HOUR A lorry leaves Stoke, travels 150km to Leeds at an average speed of 60km/h. How long did the journey take? t = 150 ÷ 60 Time = d s t = 2.5 hours s d t x MUST give UNITS Because speed was in km per HOUR

Car travels 40km in 20 minutes. What is its average speed in kph? s = 120kph s d t x