Keeping it fair

Question

  1. Sam and Sue had each bought the same kind of rubber ball. Sue said, "My ball bounces better than yours". "Prove it!" Sam replied. Which of these experiments should Sue do to find out which ball bounces higher?

    • Drop both balls from the same height a few times and see which bounces higher.

    • Throw the balls against a wall and see which bounces back the greater distance.

    • Drop the balls one at a time from different heights and see which bounces higher.

    • Throw the balls on the floor a couple of times and check how high they bounce.

Question

  1. Some children wanted to find out which of four different marbles would roll the farthest. They put a grooved metre ruler against the wall. They rolled the marbles down the ruler and measured how far they went along the floor.
rolling marbles
 
To make it a "fair test", which one of these must always be the same?

    • The size of the marble

    • The colour of the marble

    • The angle of the ruler

    • The weight of the marble

    • The width of the ruler