Friction occurs when two surfaces rub against each other and those bumps and ridges catch on each other.
A notable by-product of friction is heat.
Have your students rub their hands together quickly. It doesn’t take much hand rubbing to notice a warm feeling.
Now put a small squirt of lotion (stick to unscented stuff for this) in each students hand.
Have them rub their hands together again – much less heat is generated.
The lotion acts a lubricant – it helps fill in some of the bumps and ridges on the surface of the hands, resulting in less friction and therefore less heat.
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Presented at the 2003 New Jersey Science Convention.
