Marble Science!

CHALLENGE: How far up a ramp do you have to roll a marble from, so it travels 82cm?

This was the challenge Room 56 received to help us learn about "fair testing" in science.


DAY 1
The students took off in their groups. Some set up their equipment on the carpet, some on the tables and some on the lino.

One group set up on the carpet.

After about 10 minutes we had groups reporting they had had a roll reach exactly 82cm. "Let me see", the teachers would say, but no groups were able to repeat this result.

To reflect at the end of the lesson we recorded where the groups had to release the marble to get their 82cm roll. The 10 results ranged from 6-29cm up the ramp. They were asked, why are our results so different? The students quickly realised all the things each group was doing differently; rolling surfaces (table tops, carpet, lino, etc.), marble sizes and , most importantly, the angles the ramps were held. We started to refer to these as "variables".

DAY 2
When doing the challenge this time we made sure to limit our "variables". All groups performed the activity on carpet using marbles of the same size, and all ramps were set propped up on 4 maths text books (using Blutak, 27cm up the underside of the ramp).

Measures, cm, displayed on the ramp.

Four maths book standard height.

This time results were more repeatable. Groups could consistently roll a marble to between 81-84cm, by releasing the marble from a consistent start point.

However, we still found a difference in the height up the ramp, of the start point, between groups. Were we missing some variables? Upon further reflection students thought we should have all used the same carpet square to test on, and used the same marble to test with (surface textures, and possibly weights, were different).  Our discussion was now using terminology, such as variables and controls. Each time we identified a variable, the students came up with global settings/measures to make these controls instead, making our results more reproducible.