Homework Help: physics, PLEASE ANSWER, I really need help!

Posted by AE on Sunday, December 6, 2009 at 5:48pm.

The basal metabolic rate is the rate at which energy is produced in the body when a person is at rest. A 70.0 kg person of height 1.79 m would have a body surface area of approximately 1.90 m^2. What is the net amount of heat this person could radiate per second into a room at 19.0 degrees celsius if his skin's surface temperature is 31.0 degrees celsius? (At such temperatures, nearly all the heat is infrared radiation, for which the body's emissivity is 1.00, regardless of the amount of pigment.)

physics, PLEASE ANSWER, I really need help! - drwls, Sunday, December 6, 2009 at 5:56pm
The net rate of radiative power loss is
(Area)*sigma* [T(body)^4 - T(room)^4]

The radiation is almost entirely invisible infrared.

When using the formula, T must be in Kelvin and the "sigma" is the Stefan-Boltzmann constant, which must be explained in your tesxt somewhefre. Look it up.

The negative room temperature term takes into account the radiation of the room onto the body.
physics, PLEASE ANSWER, I really need help! - AE, Sunday, December 6, 2009 at 6:17pm
I did that but the website that I do the homework on says my answer is wrong. Here are the numbers I plugged in:
(1.9 )(5.67*10^8)((31+273)^4 - (19+273)^4)
and I get the answer is 1.37*10^18 but it says that's wrong
physics, PLEASE ANSWER, I really need help! - AE, Sunday, December 6, 2009 at 6:19pm
oh, never mind, I got it, I was using the wrong value for the constant, thanks!

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