What Is Friction?

Friction Science Lesson for Kindergarten and Elementary School Children

Use this activity to teach your child about friction. Cars, trucks, airplanes and machines all have parts that rub against one another. These parts would heat up, wear down and stop working if we didn't have lubricants. Lubricants reduce the amount of friction between two surfaces that move against each other.

What You Need

• Mixing bowl
• 4 envelopes of unflavored gelatin
• Hot water
• Square baking pan
• Vegetable oil
• Liquid dish-washing detergent
• 2 small bowls
• Stopwatch or a watch with a second hand
• Measuring cup

What To Do

In a mixing bowl, dissolve the gelatin in two cups of hot tap water. Coat the inside of the pan with vegetable oil. Pour the gelatin mixture into the pan and put it in the refrigerator until firm. Cut the gelatin into cubes about 1 inch x 1 inch. You should have about 64 cubes. Place 15 cubes into one bowl. Place the second bowl about 6 inches (about 15 centimeters) away from the cube bowl.

• Place the watch so that your child can see it. Tell her that when you say go, you want her to start picking up the gelatin cubes one at a time with her thumb and index finger (caution her not to squeeze them!). Tell her to see how many cubes she can transfer to the other bowl in 15 seconds.
   
• Tell your child to put all the cubes back in the first bowl. Pour 1/4 cup dishwashing liquid over the cubes. Gently mix the detergent and the cubes so that the cubes are well-coated. Have her use the same method as before to transfer as many cubes as possible in 15 seconds.
   
• Throw away the cubes and detergent and wash and dry both bowls. Put 15 new cubes into one bowl and pour 1/4 cup water over the cubes, again making sure the cubes are thoroughly coated. Tell your child to see how many cubes she can transfer in 15 seconds.
   
• Again, throw away the cubes and water. Put 15 new cubes into one bowl. Pour 1/4 cup of vegetable oil over the cubes. Make sure they are well coated. Have her see how many cubes she can transfer in 15 seconds.
   
• Ask your child to answer the following questions:
• With which liquid was she able to transfer the most cubes?
• With which liquid was she able to transfer the fewest cubes?
• Which liquid was the best lubricant (the slipperiest)? Which was the worst?

Follow up discussion:

Talk to your child about how cars, trucks, airplanes and machines all have parts that rub against one another. These parts would heat up, wear down and stop working if we didn't have lubricants. Lubricants reduce the amount of friction between two surfaces that move against each other.

Learn More About Friction