Idea 9of 11Builds onOne picture, three equations
Which equation
Three equations: which one do you reach for?
Today you'll discover
- how to list what a problem hands you
- how to match it to one reading of the picture
- why the unknown matters as much as what you have
Think firstGiven 2, 6 m/s and 4 s. Want: how far
Two velocities and a time, wanting how far. Which reading of the picture?
Decide first, then press Next. Name what the problem hands you, then what it wants.
The cart's velocity–time graph with its rising line unlabelled. After a prediction, its two ends are named, 2 metres per second at the start and 6 at four seconds. Then the dashed rectangle under the average, labelled 4 metres per second times 4 seconds equals 16 metres east, with the equation under the picture. The last step shows the slope triangle and asks which reading gives the acceleration.
See the whole ideathe big idea and the key word, in one place
The big idea
List the givens. Pick the equation holding them and the unknown.
For exampleThe cart gives 2 m/s, 6 m/s and 4 s and asks how far: start, end and time, wanting displacement. That is the midline equation.
Key word
- givens
- the quantities a problem states, listed with their symbols before any equation is chosen
About this modelBelow the line means moving the other way, not slowing down.
Below the line means moving the other way, not slowing down.
Ready to use it?
- Pick the equation from the givens, then solve it.