1. Speed, distance, time

2. Speed, Distance and Time
A car travels 100m in 5s. What is its average speed? 20m/s
A car is travelling at 30m/s how far does it travel in 60 seconds? 180m
What does a horizontal line on a distance time graph represent? A stationary object
What does the gradient of a distance time graph represent? Speed
Add the units to the distance time graph over the page. m and s
What was the speed of the person between 10s and 50s? 3m/s
Over which time period does the person go fastest? 80s-120s
What does a horizontal line on a speed time graph represent? Constant speed
What does the gradient of a speed time graph represent? Acceleration
Add the units to the speed time graph over the page. m/s and s
What are the units of acceleration? m/s2
How fast was the car accelerating between 0s and 40s? 0.5 m/s2
How fast did the car decelerate before coming to a complete stop? -1.5 m/s2
How far did the car travel in this time? 300m
How far did the car travel when travelling at 30m/s? 1200m OR 1.2km

3. How far Bob runs.
How fast a car is travelling.

4. A child ran out in front of a car causing the driver to make an emergency stop. The graph shows how the speed of the car changed from the moment the driver saw the child.
(i) What was the driver’s reaction time?
(1 mark)
0.7 seconds (accept 1 second)
(ii) Describe the motion of the car during the first 0.5 seconds.
Constant speed
(iii) How long did it take the car to stop once the brakes were applied?
3.3 seconds (accept 3 seconds if answer for q1 was 1 second)
(iv) The drug cannabis makes the reactions of a person slower.
Explain how the stopping distance of the car would change if the driver had been smoking cannabis.
(1) The reaction time of the driver would have been longer so the time between seeing the child and applying the brakes would have been greater.
(2) The braking distance would have been the same.
(3) The overall stopping distance would have been longer.