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\leftline{Mathematics 134 -- Intensive Calculus for Science 2}
\leftline{Quiz 9 -- April 21, 2006}
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\leftline{Your Name: $\underline{\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ }$}
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Do all work on this sheet (front and back).  You have 15 minutes.
{\it Approved calculators OK on this quiz.}
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Newton's Law of Cooling states that the 
rate at which the temperature of an object changes is 
proportional to the difference between the object's temperature
and the surrounding temperature.
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A) (5) Express Newton's Law of Cooling as a differential equation.
Call the object's temperature $T$ and the surrounding temperature 
$A$ (a constant).
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B) (10) Solve for $T$ from your equation in part A.
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C) (10)  A hot horseshoe with temperature
$200^\circ$C is placed into a large vat of water maintained at constant 
temperature $30^\circ$C.  Ten minutes later the horseshoe has cooled to 
$140^\circ$C.  How long will it take to cool off to $75^\circ$C?  
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