2. Distance-time graphs
Segment "A" of the graph shows the vehicle covering 35km distance at a steady rate.
What is happening in the other segments?
Segment "B" also shows the vehicle covering the distance at a steady rate albeit a little slower than section "A". At the 4 hour mark the section "C" the vehicle has stopped. This is obvious by the straight line. The driver may actually be having a 2 hour rest 4 hours after the journey started. Six hours after the journey commenced the vehicle speeds away to cover 40 kilometres in 1 hour. The steady rate with which it covers the distance is greater than in section "A" and "B ".

3. Distance-time graphs Diagonal line = steady speed
Curved line = accelerating
Horizontal line = stopped
Segment "B" also shows the vehicle covering the distance at a steady rate albeit a little slower than section "A". At the 4 hour mark the section "C" the vehicle has stopped. This is obvious by the straight line. The driver may actually be having a 2 hour rest 4 hours after the journey started. Six hours after the journey commenced the vehicle speeds away to cover 40 kilometres in 1 hour. The steady rate with which it covers the distance is greater than in section "A" and "B ".
Speed is the gradient of a distance vs time graph.

4. Distance-time graphs

5. Look at the cars – what do you notice about their movement?

6. Speed-time graphs Acceleration is the change in your speed:
speeding = accelerating
slowing down = decelerating
Acceleration is the gradient of a velocity vs time graph.

7. Speed-time graphs
Horizontal line = constant speed

8. Speed-time graph

9. Discuss what the graphs are telling you about the relative movements of the cars? Link this to the motion recorder shown behind the cars.

10. A car travels along a road and leaks oil at the rate of one drop every second. The distance between the drops was measured and plotted on a graph.
The distance travelled between each drop is an indication of the speed of the vehicle. The faster the vehicle goes the greater the distance between the dots.
Notice how the speed of the vehicle is constant between 4 and 7 seconds at a speed of 5m/s. Every second it covers 5 metres. Between 7 and 8 seconds the speed is also constant at 3m/s. Every second it covers 3 metres. During the first 3 seconds of its journey the car is steadily increasing its speed. Notice how every second it covers more distance than during the previous second.
The distance covered by the vehicle per time is called the speed of the vehicle.
The units can be expressed as: cm/s(centimetres per second); m/s (metres per second); Km/s(kilometres per second); Km/hr(kilometres per hour) and so on.

12. Acceleration
a, units ms-2
ms-2