Idea 9of 12Builds onHow fast, on the pathHow fast, and which way
The whole trip, or one moment
Was she always walking at the same rate?
Today you'll discover
- two legs walked at two different rates
- a whole-trip number she never actually walked at
- what a speedometer reads
LookThe leg out: six metres in four seconds
Six metres in four seconds: 1.5 metres each second on this leg.
Compare the two legs before pressing Next. Then see one number for the whole trip.
Amara's walk, built up by pressing Next. The leg east is six metres in four seconds; the leg back west is six metres in six seconds, a slower leg; then the working across the top shows the whole trip, twelve metres in ten seconds, 1.2 metres per second. Three different rates, and the last one belongs to no single leg. The last step asks how fast she is walking when the clock reads six seconds.
See the whole ideathe big idea and the key word, in one place
The big idea
A trip's rate is an average. A moment's rate is instantaneous.
For exampleHer average over the trip was 1.2 metres per second, a rate she never actually walked at: the leg out was faster and the leg back slower.
Key words
- average speed
- the whole distance divided by the whole time
- instantaneous speed
- how fast something is going at one moment, what a speedometer shows
Ready to use it?
- Tell an average from a reading at one moment.