Idea 8of 12Builds onStart to finishWhich wayHow fast, on the path
How fast, and which way
How fast, and in which direction?
Today you'll discover
- a rate that keeps its direction
- why a twelve-metre walk can have a rate of zero
- the word physics uses for it
Think firstSix metres east in four seconds
Start to finish, six metres east in four seconds. How fast, and which way?
Answer first, then press Next. The arrow, the clock, then the division worked across the top.
A walk of six metres east with no return, with the solid arrow at the top labelled six metres east and the boxed clock reading four seconds. Pressing Next adds a boxed line of working across the top: start to finish divided by time, six metres east over four seconds, equals 1.5 metres per second east. Then Amara's walk out and back with the same working, where start to finish is nothing and the rate is zero. The last step shows the dog's run and asks for its rate.
See the whole ideathe big idea and the key word, in one place
The big idea
Velocity: displacement divided by time, direction kept. Out and back: zero.
Compare them
Being ahead and being fast are different things. The runner in front here has the shorter arrow, and will be overtaken.
aheadwherefasterhow fast
Key word
- velocity
- displacement divided by the time it took, with its direction; a vector, in metres per second [direction]
Ready to use it?
- Work out a velocity, and keep its direction.