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What do I need?: 
  • A mug, glass, plastic or paper cup, or small Tupperware
  • An index card, a piece of cardstock
  • A coin, washer, or checker
What do I do?: 
  1. Place the card flat over the top of your cup or mug
  2. Place your weight on top
  3. Move the card slowly and observe what happens
  4. Pull the card away quickly while keeping it flat
Whats going on?: 

This is an example of Newton’s 1st Law of Motion: The Law of Inertia. The Law of Inertia states that an object in motion will stay in motion and an object at rest will stay at rest. The weight is at rest. When you move the card slowly, the weight moves with it due to friction acting like a grip. When you move the card fast, not enough friction builds up to create that grip and the weight stays put. It falls into the cup once the card is out of the way due to gravity


Try stacking more weights on top of the card.

Try pulling the card out even faster.

Try using your fingers to flick the card out of its place. This one takes more practice.

Can you think of ways to change the variables?

What might be affecting how well you are able to accomplish this trick?

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