My friend has a Physics problem.

[Qacer]

An ill 60 kg patient whose body has an average specific heat 3.47 joules/(gramxdeg C) must reduce her fever by 2.0 deg C. About how much "heat" must be removed from her body to accomplish this?

Answer in joules.
A. 0
B. 129
C. 416
D. 712
E. 140,000
F. 416,000


For this problem, I'm using the "cancel out the necessary units" method. I'm not sure if tis right.
I get:

(3.47 Joules per gram*Celcius) x (60,000 grams) x (2.0 Celcius) = 416400 Joules


As 200 Joules of energy is added to a gas, the gas simultaneously does 600 Joules of work. The involved process is best describe as (explain)?
A. Adiabatic
B. isothermal (Hey why cant i find this info at any physics book, does it exist)
C. Isovolumetric
D. Other these are all incorrect..

I forgot my definitions.

Thanks for any help...

Here is her picture: Pictures
She's somewhere there... By the way, that page hasn't been updated since 1998. Hehe.

 

[notfred]

I agree with the "F" answer.

 

[thEnEuRoMancER]

ad 1) F is correct

ad 2) I think the correct answer is D if the 200 Joules of energy added is heat. In an adiabatic process no heat exchange is allowed to take place so A must be wrong. In an isovolumetric process the gas cannot do any work so C is also wrong. In an isothermal process the temperature stays constant throughout the process (and subsequently the internal energy of gas). In order for the internal energy to stay constant the amount of heat added must be the same as the amount of work done, which is not the case here so B must be wrong, too.

 

[rgwalt]

<< ad 1) F is correct

ad 2) I think the correct answer is D if the 200 Joules of energy added is heat. In an adiabatic process no heat exchange is allowed to take place so A must be wrong. In an isovolumetric process the gas cannot do any work so C is also wrong. In an isothermal process the temperature stays constant throughout the process (and subsequently the internal energy of gas). In order for the internal energy to stay constant the amount of heat added must be the same as the amount of work done, which is not the case here so B must be wrong, too. >>



I second this view.

Ryan

 

[Qacer]

Thanks a bunch!

I used the same reasoning for (2).. I just wanted a confirmation. I took Physics a long time ago.

 

[Qacer]

Hey everyone,

I got another email from my friend. I don't know what to do with this problem:

her message:

I have one last question to ask u.... hope u don't mind....

An 800 pound object is suspended from a large spring scale so that the object is submerged in water. The spring scale reads 270 pounds. The volume of the object is closest to ( ) cubic feet:

A. 80.0 B. 69.1 C. 62.3 D. 52.7 E. 41.0 F. 35.5 G. 30.3

H. 22.2 I. 17.6 J. 8.5 K. 5.3



I know its goin to be the archimedes principle.... And that the bouyant force will be 530 ( is that right), the gravity will be 32 ft/sec squared, the density of water is 62.4 ft/sec squared.

I got the bouyant by subtracting the actual weight and the weight in the water....

 

[Haircut]

Difference between object in air and in water is 530 lbs. The object displaces 530 lbs of water (assuming air has negligible mass).
So we need to find the volume of 530 lbs of water, this is then the volume of the object.

I'll let you do this as I can't be bothered working in those stupid backwards units.

 

[Qacer]

Ok, thanks for the tip! I'm going to search google for this volume relation. hehe..