Experimenting with a bowl full of hot soup is likely to be messy. We propose that we can substitute a circular carpenter's level. Sitting on the table, the bubble is at the center; when you bump it, the bubble goes off center. If the bubble goes all the way to the edge, you have spilled the soup.
1. Explore moving the level by sliding it along a level surface. What is the fastest way to move it from one place to another (a half-meter away), without "spilling the soup"? Of course, the level is not moving at the beginning or end. Describe how you have to move the level in order to get it from one place to another quickly, while still keeping the bubble close to the center.
2. Practice sliding the level on its card in a straight line at constant velocity. What does the bubble do while the level is moving at constant velocity?
3. Which way does the bubble go while you are pushing on the level to make it start moving?
4. Which way does the bubble go while you are slowing the level down?
5. Place a marker (a piece of paper, or a sticky note) on the table, and move the level around the marker in a circle. What does the bubble do? Observe the cases that the motion is slow or fast, and that the circle is small (10 cm radius) or larger (30 cm radius).
6. Think about all the observations you have made with the level. What does the bubble tell you about the motion of the level? How is this related to how you are pushing on it?
Check the box when you are done: