Suppose a human could live for two hours (120 minutes ) unclothes in a

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Homework Help Overview

The discussion revolves around the thermal conductivity of air and water and its implications for human survival time in different environments at a constant temperature of 45°F. The original poster attempts to relate the thermal conductivities of air and water to determine how long a human could survive in water compared to air.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the relationship between thermal conductivity and survival time, questioning the calculations and the meaning of the variables used. There is confusion regarding the original poster's mathematical approach and the interpretation of the results.

Discussion Status

Some participants have provided feedback on the calculations, with one suggesting that the revised calculation appears more reasonable. There is an ongoing examination of the assumptions made in the original calculations and the need for clarity in the units used.

Contextual Notes

Participants are discussing the implications of thermal conductivity in the context of human survival, with specific attention to the temperature and medium (air vs. water). There is a noted lack of consensus on the interpretation of the calculations and the variables involved.

manal950
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Suppose a human could live for two hours (120 minutes ) unclothes in air at 45 F . How long could he live in water at 45 F ?

how do the thermal conductivities of water and air compare ?
Air : k = 0.0251 W/mC ,
water = k = 0.597 W/mC


my answer

now for conduction we will say that

-k(air ) .A(dT/dx) dtime = -k(water ) .A(dT/dx) dtw

= 0.025 X 2 / 0.597

= 0.083 second
 
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manal950 said:
= 0.025 X 2 / 0.597

= 0.083 second

Huh?

No idea what is what of what nor how you got the number you got.

What is 2?

And your math is incredibly off.
 
sorry

= 0.025 X 120 / 0.597

= 5.04
 
That looks much more palatable.

It won't hurt to include units in your answer.
 

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