The number 2

ome Experiments and Observations El. If there is a park nearby containing a freely rotating child's a. Does the ruler balance exactly at its midpoint? What merry-go-round, take some time with a friend to observe does this imply about the ruler? some of the phenomena discussed in this chapter. In par- b. Using a nickel as your standard, what are the ratios of ticular, make these observations: the weights of pennies, dimes, and quarters to that of a, What is a typical rotational velocity that can be achieved the nickel? Describe the process used to find these with the merry-go-round? How would you go about ratios. measuring this? c. Is the distance from the fulcrum necessary to balance b. How long does it take for the merry-go-round to come two nickels on one side with a single nickel on the op- to rest after you stop pushing? Could you estimate the posite side exactly half the distance for the single nickel? frictional torque from this information? What other in- How would you account for any discrepancy? formation would you need? c. If you or your friend is riding on the merry-go-round, HE3. You can make a simple top by cutting a circular piece of what happens to the rotational velocity when you move cardboard, poking a hole through the center, and using a inward or outward from the axis of the merry-go-round? short, dull pencil for the post. A short, wooden dowel with How do you explain this? a rounded end works even better than a pencil. a. Try building such a top and testing it. How far up the Create a simple balance using a ruler as the balance beam pencil should the cardboard disk sit for best stability? and a pencil as the fulcrum. (A pencil or pen with a hexago- b. Observe what happens to the axis of rotation of the top nal cross section is easier to use than one with a round cross as it slows down. What is the direction of the angular- section.) momentum vector, and how does it change