Comments on Physics 7B (Spring 2002) Lectures
Lecture on Jan. 23 (Wed.)
Relation between tempeatures measured in Celsius and Fahrenheit can be written as
T(deg. C) = A + B x T(deg. F) - Eq.(1)
where A and B are constants.
We know that 100 deg. C is equal to 212 deg. F, and 0 deg. C is equal to 32 deg. F. Let's write them using Eq.(1).
100 deg. C = A + B x (212 deg. F) - Eq.(2)
0 deg. C = A + B x (32 deg. F) - Eq.(3)
Subtract Eq.(3) from Eq.(2)
100 C-deg. = B x (180 F-deg.)
B = 5 / 9
Apply B = 5/9 to Eq.(3)
0 = A + 5/9 x (32 deg. F)
A = - 5/9 x (32 deg. F)
Apply A and B to Eq.(1)
T(deg. C) = 5/9 x [ T(deg. F) - 32 deg. F ]
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