Wednesday, February 19, 2014

Sliding Discs: Making a Surface Slippery

Friction can be a difficult concept to explain (even to adults).  The best we can do in these early years is help kids develop an intuition about how you can change a surface and therefore change how something will interact with it.  One fun way to do this is by looking at how far an object travels and then observe what happens after the application of a lubricant, such as oil or soapy water.  The kids can compare changes in the distance an object travels.

One fun way to investigate what happens when you make a surface slippery is with a sliding game!

On your marks... get set... GO!!

Today was our first day of really nice weather for the year so we decided to take our scientific quest outside.  Our race tracks were long sheets of foil raised on the sides and our race cars were plastic discs.

Jelly Bean and Jumping Bean are racing little discs down a foil track by giving them an initial push.  The foil track does not have anything on it, and they still slid the discs pretty far.  Jumping Bean looks pretty competitive trying to slide her disc.

A little teamwork was used as the girls measured how far each of the discs slid down the track.

Next, we sprayed a combination of hand soap and water to create a lubricant which we thought would reduce the friction between the foil and disc.  We are hoping the disc will slide even further than on the dry foil.

It's off the track!  Jumping Bean's track was so slippery that the disc slid right off.  The lubricant worked!  The soapy surface made for a slippery track for our discs, and they went much further than on the dry foil.     

Not only did the girls have fun creating a slippery, soapy track, but they also made a great connection.  Jelly Bean said, "Yep, and that's why we don't run at the pool.  The slippery water will make you slip right off the side."  I just smile when I know they have learned something, and they can relate it to our everyday life!


  • foil
  • something to slide, we used a disc from a game but coins could work as an option
  • water
  • hand soap
  • ruler or measuring tape

  1. Create a track using foil.  Fold the sides up to help prevent the disc from sliding off the side.
  2. Place the disc at the top of the track and slide it by giving an initial push.
  3. Measure the distance the disc travelled.
  4. Premix equal parts of water and hand soap and pour onto the track.  Spread by hand to ensure the whole surface is covered.
  5. Place the disc at the top of the track and slide it again. 
  6. Notice how much further the disc travelled when there was a lubricant (soapy water) on the track.
  7. Measure the distance again.  
    As an advanced activity with an older child you could find the difference between the first slide and the second slide.  (We did not find the difference.  The girls were more excited about how far off the track they could make the disc go.)

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