A diver is used to illustrate the concept of a negative number scale. The surface of the diver's swimming pool is set to 0 on the measuring scale. As he completes his dive, he travels from plus 10 metres to minus 6 metres and back to 0.
Could be used to introduce or reinforce the concept of adding positive numbers to negative numbers on a number line. Provide the students with a number line on a piece of paper with values ranging from -10 to 10, where each number represents a metre. Students could then draw a line through '0' to represent the ground, then branches of a tree which are 'X' number of metres high and roots which are 'X' metres underground.