## Marble mania

Classroom Activity for 11-14

What the Activity is for

Discussing fastest and shortest time.

The purpose of the activity is for pupils to recognise that speeds can be ranked by comparing times, provided that the distance travelled is the same. This being the case pupils should appreciate the fact that the shortest time means the greatest average speed.

What to Prepare

- a simple race track – curtain rail, or the space between two metre rules
- marbles (or table tennis or polystyrene balls) and straws
- metre rules and stop clocks
- choose the materials to ensure that pupils are not timing unrealistically short events

What Happens During this Activity

Pupils blow the marble along the race track as quickly as possible. Pupils compete in groups of four. One pupil should blow the marble while the others record the time taken to complete a 200 centimetre course. The winner from each group enters the final stages of the competition.

**Safety note: **Be aware of pupils with significant asthma or breathing difficulties.

#### Making and using measurements

In this activity it is not intended to have competitors racing against one another at the same time. Pupils can see the need to agree on reliable measurements to find the winner. The marble with the greatest average speed wins. Of course you don't need to know the speed. The shortest time wins. It is important in our context to extend the task to the calculation of average marble speed. Each group will therefore need to keep a record of their results. Depending on the age and ability of the pupils, you may provide a structured results table or encourage pupils to construct their own.

Some pupils will struggle with using the equation for speed. They might lack confidence with mathematics. You might want to try an approach which is based on simple proportions.

For example:

Teacher: The marble travelled 200 centimetre in 5 second – how many centimetres would it travel in 10 second? How many centimetres in 1 second?

Once pupils become familiar with the idea that speed is the distance travelled in 1 second

, then solving problems by proportion can often become more straightforward.

Teacher: If I travel 60 metre in 10 second, how far will I travel in 1 second?

Mike: 60 metre divided by 10 second, so you travel 6 metre in 1 second.

Teacher: What is my speed?

Jaz: 6 metre every second, which is 6 metre / second.

For problems of this type, pupils are not directly using the equation for speed, they are calculating speed by proportion, knowing its units.

Part of the solution is also to do lots of examples using the equation – first on the board with the whole class suggesting the next step, then in small groups working on problems, and finally on an individual level. Some pupils may struggle with recalling the equation for calculating speed. By having the equation written large and displayed on the wall, you remove this hurdle. At this stage it is not necessary to engage in rearrangement of the equation to calculate distances. This will come later.