215H Puzzle

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(Last Name and Last 4 digits of your SSN together)

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	M1	M3	M6
Dr E Patterson
Capt Summers

TIME IN:

Puzzles will be posted at 2000 (8pm) each Sunday evening. Puzzle solutions are due by 0630 on the Tuesday or Wednesday M-day of each week (on the day we have class).
Answers must be accompanied by an explanation of valid reasoning. Please remember that the answer alone isn't enough! A correct answer without correct reasoning will not earn you credit.
Each week, the first student to submit a correct answer will receive 50 VIP points and an added surprise (to be disclosed during the first puzzle week). Students who submit subsequent correct answers and correct explanations will earn 30 VIP points.
Please enter your solution in the text area at the bottom of this page. When you are satisfied with your response, click the SUBMIT button at the bottom of this page.

"When Bobbing Met Sally"

Little Sally is floating peacefully in her small red plastic boat, at the position marked "A" in the figure to the right. The lake is calm and the day is sunny. A motorboat speeds by, about 30 m off the shore, and the waves reach the shore about half a minute later. Suddenly, little Sally's older brother and sister decide to give Sally some fun. Each sibling is in a rowboat firmly tied to moorings out in the lake, as shown in the figure. They each jump up and down in their respective rowboats, bobbing up and down in synch together, about 15 times every half a minute. Soon large waves are emanating from each of the bobbing boats, and the older brother and sister are giggling fiendishly.
Sally's father, seeing the situation, and having taken the equivalent of Honors Physics 215 (!), does some quick thinking and moves Sally to the position marked "B" in the figure.
Sally likes to float in calm water. Does Sally's father do Sally a favor by moving her?

Don't forget to fully explain your reasoning! Please explain as clearly as possible.

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