Friction

Children in 4G have been testing different materials to see which one slows the car down the most (has the most friction).

When we did it in small groups we didn't all get the same result, so today we tried it again, the whole class working together.

These are the results we got:

So, we found out that there's the most friction with the bumpy carpet. And the least friction with the rubber.

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In 4B we did the same question but in a different way.

Here are our results:










Good news!  We also found that the bumpy carpet (purple carpet) had the most friction.  The smooth rubber had the least amount of friction.

However, we were surprised at our results for the two types of sand paper.  We had talked about the textures and really thought the rough sand paper (yellow sand paper) would have the most friction.  Many of us were wrong!

Friction - settling a question

Talking about friction, we rubbed our hands across the desk and the carpet. "Which is easier?" asked Mr Gregg. We couldn't agree: some thought the desk, some thought the carpet.

So... a scientific experiment. Measure the force it takes to move a stone in a bag on the two surfaces. Which would take more force?

The carpet took more force: 10 Newtons, compared to just 5 on the desk. There must be more friction on the carpet.

But Tibo said, "It's not fair. The bag makes it easier on the desk."

Half the class agreed. So we untied the bag, and tried the stone directly on the two surfaces:

This time it took 10 Newtons on the carpet, and only 2 Newtons on the desk. There's definitely more friction on the carpet!

Now the only question is, why didn't we agree that in the beginning?