Motion graphs
Reading distance-time graphs (gradient is speed, a flat line is stationary) and speed-time graphs (gradient is acceleration, area is distance), with the numbers worked out on screen. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
Practice
- Check yourself: Motion graphs – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it.
Transcript
This is a distance-time graph. Time is on the horizontal axis and distance is on the vertical axis. A straight sloping line means constant speed.
The gradient of the line is the speed. For the first twenty seconds, the distance rises by forty metres. Forty divided by twenty is two metres per second.
A flat line means the distance is not changing. The object is stationary.
A steeper line means a higher speed. A line that goes down means the object is coming back.
Now a speed-time graph. Speed is on the vertical axis. A line that goes up means the object is accelerating. A flat line means a constant speed.
A line that goes down means the object is decelerating. A line at zero would mean the object is stationary.
The gradient of a speed-time graph is the acceleration. The speed rises by twenty metres per second in ten seconds. Twenty divided by ten is two metres per second squared.
The area under a speed-time graph is the distance travelled. Add up the area of the three parts: one hundred, four hundred and one hundred. The distance is six hundred metres.
Remember. On a distance-time graph, the gradient is the speed. A flat line means stationary. On a speed-time graph, the gradient is the acceleration. And the area under the graph is the distance travelled.
More in this series
6:12P1 Motion: key vocabulary
Twelve key words for IGCSE Co-ordinated Sciences topic P1 (motion), with the Vietnamese meaning, how to say each word, a picture and an example. Ends with a test section, and a typing trainer on the site that also practises twelve general science words.
2:41Speed and velocity
How to measure distance and time, the speed formula with a worked example, average speed for a journey with a stop, and the difference between scalar speed and vector velocity. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
5:41P1 quiz: motion
Ten think-time questions on speed, average speed, scalars and vectors, distance-time graphs and speed-time graphs.