Chapter 15, Problem 40PCE

Predict/Explain Referring to Example 15-12, suppose the flask with the wood tied to the bottom is placed on a scale. At some point the string breaks and the wood rises to the surface where it floats. (a) When the wood is floating, is the reading on the scale greater than, less than, or equal to its previous reading? (b) Choose the best explanation from among the following:

1. I. The same mass is supported by the scale before and after the string breaks, and therefore the reading on the scale remains the same.
2. II. When the block is floating the water level drops, and this reduces the reading on the scale.
3. III. When the block is floating it no longer pulls upward on the flask; therefore, the reading on the scale increases.