Lesson 9 of 11
The big picture
Show on a big screenEach idea is a number to find or a shape to read.
| Idea | Remember | Example |
|---|---|---|
| Where it is | Position is distance and direction from a reference point. Right of the point is positive. Left is negative. | P is +30 m from S, and −60 m from Q |
| Distance and displacement | Distance is the whole length of the path. Displacement is the change in position, with a direction. | 120 m run, displacement +40 m |
| Speed and velocity | Average speed is total distance divided by time. Average velocity is displacement divided by time. | 120 ÷ 20 = 6 m/s, and 40 ÷ 20 = 2 m/s |
| Acceleration | Acceleration is the change in velocity divided by the time taken. Its unit is metre per second squared. | (13 − 4) ÷ 6 = 1.5 m/s² |
| Steady and changing motion | Uniform motion covers equal distances in equal times, however short. Otherwise the motion is non-uniform. | Gaps of 1, 3, 5, 7 m: speeding up |
| Reading a graph | On a position-time graph, the slope is the velocity. On a velocity-time graph, the slope is the acceleration. These shapes are for motion in one direction. | A steeper position-time line is faster |
| Area under the line | The area under a velocity-time line is the displacement. For constant acceleration, v = u + at and s = ut + ½at². | 24 m under the line |
| Round and round | In uniform circular motion, the speed is constant. The direction of the velocity keeps changing. So the motion is accelerated. | 44 m lap in 22 s is 2 m/s |
Chapter 4 of your book, Exploration, is Describing Motion Around Us. Read the chapter this week, with these eight ideas beside you.