The Quarter on the Card

Today, you tried to move an index card perched on top of a cup of water, without moving the quarter that was lying on the card.

• Some people moved the card with the quarter on top. The quarter traveled with the card.
• Some people quickly pulled or pushed the card out of the way, and the quarter dropped—into the water!

Once again, think about what happened to the quarter.
When it was on the card, it was still—not moving at all. If you did nothing, it would continue to be still on top of the card.

How did the quarter move? It moved when the card was taken away. The quarter dropped.

Why did the quarter move?

Gravity pulled it down.

Why didn't it move before we moved the card? Wasn't gravity working then?

What force was holding the quarter up on top of the card?

What force stopped the quarter from plunging directly through the card—and cup and table!—to the center of the earth?

I was very impressed with all of you today. You really put some thought and effort into trying to figure out the puzzle and to ask investigable questions.

Remember:
Investigable: You can figure out the answer yourself.
Research: You have to ask someone else what the answer is.

I'm even more looking forward to our year.
Thanks,
Allison