You are a member of a production crew filming a nature explorer in the Rocky Mou
ID: 2244787 • Letter: Y
Question
You are a member of a production crew filming a nature explorer in the Rocky Mountains. The explorer needs to swim across a river to his campsite. By watching debris flowing down the river, you estimate that the stream is flowing at 1.43 mph. In still water, he can swim at 1.65 mph. At what angle with respect to the shoreline would you advise him to swim to travel directly across the stream to his campfire?The water is near freezing in temperature. Typically a human can only swim in such water for about 5 minutes before hypothermia sets in. Calculate the time the explorer spends in the water if the river is 90.7 feet wide.
Explanation / Answer
the component of the swimmers velocity must cancel out the rivers velocity to travel directly across the stream to his campfire
therefore 1.65cos (theta)=1.43
theta =29.926 degrees
he must swim at an angle of 90+29.926=119.926 degrees to the rivers velocity
his component of velocity across the river is 1.65sin(29.926)
=0.823 mph = 0.823*5280/3600 = 1.207 ft/s
given width of the river = 90.7 ft.
therefore time taken to reach across the river = 90.7/1.207 = 75.144 s
which is less than 5 min ...
hence he wont suffer from hypothermia
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