In IGCSE Physics, you should be able to interpret graphs describing motion 😉

1. Distance-time graph

Points to remember:

1. average speed = distance moved / time taken
2. The slope of the distance-time graph represents the average speed of travel. The steeper the graph, the faster the travel.
3.  A horizontal line means the object is not moving.

Let's take a look at an example of a graph showing the distance moved by a toy car!

• Section A: It took 20 seconds for the toy car to travel 1m. The average speed is 1m/20s=0.05m/s.
• Section B: The toy car stayed stationary for 10 seconds.
• Section C: It took 5 seconds for the toy car to travel 2m. The average speed is 2m/5s=0.4m/s.
• Section D: The toy car stayed stationary for 10 seconds.

The car traveled fastest during section C.

2. Velocity-time graph

Points to remember:

1. acceleration = change in velocity / time taken
2. The slope of the velocity-time graph represents the acceleration.
3. The area below the velocity-time graph is equal to the distance traveled.

Let’s take a look at an example of a graph showing the velocity of a car!

• Section A: The car was stationary initially but accelerated to 20m/s for 10 seconds. The acceleration is (20m/s - 0m/s) / 10s = 2m/s².The distance travelled during section A is 0.5 x 10s x 20m/s = 100m. 
• Section B: The car ran at a constant velocity of 20m/s for 20 seconds. There was no acceleration. The distance travelled during section B is 20s x 20m/s = 400m.
• Section C: The car decelerates gradually from 20m/s to a stop for 40 seconds. The acceleration is (0m/s - 20m/s) / 40s = -0.5m/s². The distance travelled during section C is 0.5 x 40s x 20m/s = 400m.

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