A skier wears a jacket filled with goose down that is 15mmthick. Another skier wears a wool sweater that is 5.0mmthick. Both have the same surface are

Clifland

Clifland

Answered question

2021-03-25

A skier wears a jacket filled with goose down that is 15mmthick. Another skier wears a wool sweater that is 5.0mmthick. Both have the same surface area. Assuming thetemperature difference between the inner and outer surfaces of eachgarment is the same, calculate the ratio (wool./goose down) of theheat lost due to conduction during the same time interval.

Answer & Explanation

jlo2niT

jlo2niT

Skilled2021-03-27Added 96 answers

The rate of heat flow through a conductor is:
H=(kAL)T where k is the conductivity of the material, A is the surface area, L is the thickness
You can write this for wool sweater and for down jacket:
Hw=(kwALw)T and Hd=(kdALd)T
And take the ratio of these equations:
(HwHd)=kwLwkdLd=kwLdkdLw
my book doesnt have the k values for wool ordown, but yours must have them if its asking this question. Popthem in and calc the answer. Notice the units drop out and you willjust have a number that represents how much more heat is lost persecond through the sweater than through the down.

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