This investigation was inspired by the old fashioned Soap Box Derby races we enjoyed as children ourselves! Today, your children will experiment with gravity by changing one variable – weight – as they test how balls of the same size roll differently down two identical ramp courses. They will come to recognize and understand that in a race between two or more identical balls, the heaviest one will always travel the fastest when all other factors remain equal.

To Prepare for This Investigation:

  • Prepare a collection of balls of the same size but of varied weights. Examples; wooden balls, rubber balls, steel balls, and plastic.
  • Then, invite children to set up two identical ramp courses. An easy way to do this would be to use two ramp pieces of the same length and prop them both up on the same tool to create an incline. For example, you can prop them both on the same sized block, chair, or box.
  • Lead a discussion using the following prompts to fuel inquiry and action.

Prompts for Guided Exploration:

  • Try measuring the weight of the different balls using only your hands.
  • How do their weights compare? Which is heaviest? Which is lightest?
  • Which ball do you think will travel fastest? Why?
  • Let’s find out the answers to our questions using the ramps – we can compare two balls at a time.
  • How can we tell for sure that one ball is traveling faster than another?
  • What did you find out? Did anything surprise you?


  • Force
  • Gravity
  • Weight
  • Speed 
  • Distance

Children’s Books:

Related Products:

Discovery Ramps

Wood Balls

See Inside Pipe

Discovery Balls