How can distance be measured?
In the past people measured length with parts of the body: the span (from thumb tip to little-finger tip on a spread hand), the cubit (elbow to fingertip), the fathom (arms spread), the inch and the foot. Their size differed from person to person, which caused problems in work. More than 200 years ago in France one unit for everyone, the metre, was agreed. Today almost the whole world measures length in metres. 1 km = 1000 m; 1 m = 10 dm = 100 cm = 1000 mm. The path is the distance a body travels along its line of motion. The displacement is the shortest segment joining the start and end points. If you walk to school by a winding way the path is long but the displacement is the short straight line. Length is measured with a ruler, tape measure or metre stick.
Measure a desk with your own span and fathom, compare with a classmate, then measure in centimetres with a ruler. Why did the results differ? Draw the way from home to school and mark the displacement segment.