Question 222093
A submarine traveling at 240 mph is descending at an angle of depression of 5 degees. How many minutes, to the nearest tenth, does it take the submarine to reach a depth of 80 feet? 
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Starting from what depth?
Subs don't go 240 mph.  Nothing in the water does.
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I'll assume you mean from the surface, and accept the 240 mph (subs don't use mph, either, they use knots). Jeez
240 * sin(5º) = ~20.917 mph vertical
= 20/917*(22/15) ft/sec = 30.679 ft/sec vertical
80/30.679 = ~ 2.608 seconds