+28 The elevation of an underwater cave is -120 feet relative to sea level. A submarine descends to the cave. The submarine’s rate of change in elevation is no greater than -12 feet per second. How long will it take to reach the cave?
Using Dimensional Analysis:
You have 'feet' (-120) and 'Feet per Second' , or feet/sec (-12) and you want to find time in seconds for the submarine to reach the cave.....
If you divide 'feet' by 'feet/sec' what do you get?
(feet)/(feet/sec) = feet x sec/feet = sec (time) So if you substitute the values you have into this equation, you will wind up with the time it takes for the sub to reach the cave:
(feet)/(feet/sec) = (-120)/(-12/sec) = 10 Seconds
OR using the 'Rate Equation' : Rate = Distance/Time Rate = -12 feet/sec Distance = -120
Substitute into the equation and solve for Time
-12 = -120/time
Time (-12) = -120
Time = (-120)/(-12) = 10 Seconds
