What effect does friction have on rolling marbles?

WHAT IS FRICTION?
Friction occurs whenever 2 surfaces move against each other. Friction tends to slow movement down.

Sometimes we want lots of friction (eg - so car tyres grip the road, so our shoes don't slip on the floor, so our hands don't slip off the cricket bat).

Sometimes we don't want friction (eg - on a water slide, when we are skiing or ice-skating).

This week the middles have been finding out about which type of surface has the most friction. We tested this by rolled a marble down a ramp then onto different types of surfaces. When the marble stopped rolling we measured the distance it had rolled.

The test surfaces were:

• carpet
• cardboard
• newspaper
• towel

Which surface do you think let the marble roll the furthest?

This is what the marble ramp looked like. In this photo we are testing the cardboard race track.
We let the marble go at the top and watched it zoom down.

Next we had to measure the distance that the marble rolled. We had to use our maths skills to measure accurately and add up the measurements when the marble rolled further than the length of the ruler.The whole team had to work together on this task.

WHAT DID WE FIND OUT?

We found out that the cardboard race track let the marble roll the greatest distance. We think this is because the cardboard is really smooth so there is not much friction gripping onto the marble to slow it down.

The worst race track was the towel. The towel is really rough and has lots of fibres sticking up. These fibres grip onto the marble creating lots of friction. The marble can't roll very well at all.