This chapter studies motion: distance and displacement, speed and velocity, acceleration, distance – time graphs, speed – time graphs, centre of gravity and stability. It begins with a simple observation: when an object travels from one place to another, it reaches faster if it travels along the straight line path, because the straight line path is the shortest distance between two points.
1. Distance and Displacement
- Distance – the total length of a path taken by an object to reach one place from another place.
- Displacement – the shortest distance from the initial position to the final position of an object.
- Both distance and displacement possess the same unit. The SI unit of distance and displacement is the metre (m).
Example from the chapter
A person moves between two places A and B. Along the first path he travels 10 km; along the second path he travels 7 km. The shortest distance between the two places is 5 km (the third path). So the distance depends on the path taken, but the displacement is 5 km (in east direction). In another figure, an object travels a total distance of 120 m, but its displacement is only 40 m (south-east direction).