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Watch Out ...

They're On aCollision Course!

Have you ever wondered why friends have pillow-fights at slumber parties and not rock fights? Duh. Rocks are heavy. When you throw them, you can do serious damage. They hit things with great force. Friends don’t do that. Pillows don’t hit as hard, even though thrown by the same person.
Try this experiment to see what happens when objects hit each other.


  • Five or six objects that will roll:
    • Large and small marbles
    • Cork
    • Croquet ball
    • Toy car
    • Billiard ball
    • Marshmallow
    • Rubber ball
  • Paper
  • Pencil


  1. Pick 5 or 6 objects that have different weights and can roll.
  2. Find a flat spot. Pick one object to roll into another. Make a prediction first about what will happen.
  3. Roll the objects. Record your observations.


Draw a cartoon of one object vs. another, as if they are in boxing or wrestling matches. Give each a personality and some lines to say. Include at least four frames.


What did you learn?

  1. If a heavy object is rolled into a light one, what happens?
  2. If a very light object is rolled into a very heavy one, what do you see?
  3. What can you say about how heavy an object is and how it affects what it is rolled into?

Download the plug-ins: Get Adobe Acrobat Reader, and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 3rd grade science core.

Updated October 24, 2008 by: Glen Westbroek

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