1. DISTANCE-TIME GRAPHS

2. The steepness of a distance-time graph represents the speed.
A horizontal line shows that
the speed is zero.
time
distance
The steeper the line is,
the greater the speed.
A straight line shows that the
speed is constant (steady).

3. Example 1
150
distance from home (km)
100 50 75
time (t hours) 1 1 2 3 4 5
The distance-time graph shows the journey of a car.
a Calculate the speed of the car during the first hour of the journey.

4. Example
150
distance from home (km)
100 50
1.5 50
time (t hours) 1 2 3 4 5
The distance-time graph shows the journey of a car.
b Calculate the speed of the car between t = 1.5 and t = 3.

5. Example
150
distance from home (km)
100
125 50 2
time (t hours) 1 2 3 4 5
The distance-time graph shows the journey of a car.
c Calculate the speed of the car between t = 3 and t = 5.

6. Example
150
distance from home (km)
100 50
time (t hours) 1 2 3 4 5
The distance-time graph shows the journey of a car.
d Calculate the average speed for the whole journey.

7. Example
150
distance from home (km)
100 50
time (t hours) 1 2 3 4 5
The distance-time graph shows the journey of a car.
e Explain what is happening between t = 1 and t = 1.5.
The line is horizontal which means that the speed is zero.
So the car is stationary (i.e. not moving).