Question

The phenomena: Three rocks of equal mass are thrown with identical speeds from the top of the same building (identical height). Rock X is thrown vertically downward, rock Y is thrown vertically upward, and rock Z is thrown horizontally.

 The Question: Which rock has the greatest speed just before it hits the ground? Assume air resistance is negligible.

 a) Make a prediction based on your prior experience.

 b) Does the question involve parameters that you know to be indicators of the change in an energy systems? Which energy systems and what are the indicators?

 c) Rock X: Construct an energy-system diagram for rock X, which is thrown straight down. Write out the expression for energy conservation, based on your energy-system diagram, as AE's; then substitute in algebraic symbols for the different energy systems. You may try to solve it for the final speed, vi, in terms of all over parameters.

 d) Rock Y: Now, without actually writing anything down, consider what would be different in your energy-system diagram for Rock Y. How about the line of algebra involving the algebraic symbols anything different? In terms of the Energy-Interaction Model are there any differences? Yes or No? Are you 100% sure?

 e) Rock Z: Repeat for rock Z. Any differences in the model? Yes or No?

 f) Do you believe that conservation of energy holds in these three phenomena? Another way to ask this: Does the particular energy model you developed apply to all three cases? If yes, what does conservation of energy tell you about the final speeds of the three rocks with 100% confidence?

 g) How do you reconcile your result in (f) with your intuition in part (a) above? Why don't the differences between the rocks matter to energy conservation? Try to be as explicit here as you. can be. This is what we will focus on in the FNT follow-up in DL.

Answer 1