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tensa zangetsu [6.8K]
2 years ago
8

Newton's Law of Cooling states that the rate of change of the temperature of an object, T, is proportional to the difference of

T and the temperature of the region, TR or dT over dt equals k times the quantity T minus T sub R end quantity. An object with core temperature of 1200°F is removed from a fire and placed in a region with a constant temperature of 80°F. After 1 hour, its core temperature is 830°F. What is the object's core temperature 4 hours after it is taken off the fire? (1 point)
Mathematics
1 answer:
maria [59]2 years ago
5 0

Answer:

  305 °F

Step-by-step explanation:

The core temperature of the object after 4 hours can be found using an exponential decay formula to model the decay of the difference between core temperature and ambient.

<h3>Cooling Model</h3>

The solution to the differential equation described by Newton's law of cooling is the exponential equation ...

  y = ab^t +c

where 'a' is the initial core temperature difference from ambient, 'b' is the decay factor of that difference in 1 unit of time period t. 'c' is the ambient temperature.

For this problem, the ambient temperature is c=80, and the differences of interest are ...

  a = 1200 -80 = 1120

  b = (830 -80)/1120 = 75/112

Using these values in the model gives ...

  y = 1120(75/112)^t +80 . . . . . . where y(t) is the core temperature at time t

Note that units of time are hours.

<h3>Application</h3>

We want y when t=4.

  y = 1120(75/112)^4 +80 ≈ 1120(0.20108) +80 ≈ 305.212

The core temperature after 4 hours is about 305 °F.

__

<em>Additional comment</em>

The differential equation will have a solution of the form ...

  T-T_R=(T_0-T_R)e^{kt}

where k = ln(75/112) ≈ -0.40101

In the above, we defined b = e^k = 75/112. Accuracy with this fraction can be better than using a truncated value of k.

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3a)

<h3>Answer: The sum of a+b+c+d is equal to 220</h3>

-------------

How I got this answer:

a+b+e = 180

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angles 'e' and 'f' are marked in the attached drawing below (see figure 1)

Add the two equations to get

(a+b+e)+(c+d+f) = 180+180

a+b+e+c+d+f = 180+180

a+b+e+c+d+f = 360

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a+b+c+d = 360-140

a+b+c+d = 220

==========================================

3b)

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==========================================

4

<h3>Answer: 290</h3>

---------------------

Explanation:

Check out the attached image figure 2.

Angle DAE is given to be 30 degrees. Angle ADC is also equal to 30 because they are alternate interior angles.

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Therefore the purple angle marked in that diagram is 180-x = 180-110 = 70

The reflex angle to the 70 degree angle is 360-70 = 290

which is the shaded angle we want to determine

5 0
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