You are driving down a straight highway at 20 m/s (72 km/h) on a foggy night. Suddenly you see a truck stopped directly in front of you a distance d down the roadway.

Graph of v vs t


The horizontal line between zero seconds and one second represents the constant velocity before you react. The slope of the line thereafter is -4 m/s/s. In other words it falls by 4 m/s for every second you go right along the time axis. Thus you could plot points
16 m/s 2 s
12 m/s 3 s
and so on.
Then draw a straight line through those points down to the axis where v = 0.

Analysing the graph

You can now analyse the graph to answer part (a)

Part a

(a) What distance will you have travelled after 1 s? ... After 2 s?
The distance travelled in the first second is represented by the area on the graph bordered by four lines
  1. The line showing your velocity
  2. the v=0 line,
  3. the t=0 vertical line and
  4. the t=1 s vertical line.

To find the distance travelled between 1 s and 2 s find the area on the graph bordered by four lines

  1. The line showing your velocity
  2. the v=0 line,
  3. the t=1 s vertical line and
  4. the t=2 s vertical line.
Divide this area into a triangle and a rectangle. Then add the distance traversed betweeen 1 s and 2 s to that traversed between 0s and 1 s which you calculated first.

What to do

Identify the areas which represents the distance travelled during the between 0 s and 1 s and between 1 s and 2 s. Shade them. Find their areas.
Go back
More help
Check my answer