Position: how we know it moved
To know that something moved, we compare its position with things around it. A position is described using a reference point, a thing that stays still, such as the school gate, a lamp post or a wall. “The ball is 3 metres from the wall” tells us the position. If, a few seconds later, the ball is 7 metres from the wall, its position has changed, so it moved. Motion is a change of position over time. Whether something seems to move depends on the reference point. Mariam sits on a bus: compared with her seat she is not moving, but compared with the trees by the road she is. To measure a position, we use a tape or a ruler from the reference point, and we write the distance and the unit.
| Time | Distance from the wall | Did it move? |
|---|---|---|
| 0 s | 3 m | — |
| 3 s | 7 m | yes: 4 m farther |
Where is the car? With a grown-up, tape a start line on the floor. Roll a toy car gently and mark where it stops every second (a grown-up counts the seconds aloud). Measure each mark from the start line with a tape and write the distances in a table: 1 s, 2 s, 3 s. Did the car move? How do you know? What was your reference point? Keep the floor clear and do not roll it toward feet.