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1. Distance-time graph
Points to remember:
- average speed = distance moved / time taken
- The slope of the distance-time graph represents the average speed of travel. The steeper the graph, the faster the travel.
- 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:
- acceleration = change in velocity / time taken
- The slope of the velocity-time graph represents the acceleration.
- 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.