Re: Stop using calories?

[John Mallinckrodt <ajmallinckro@CSUPomona.Edu>]

On Thu, 18 Sep 1997 herbgottlieb@juno.com wrote:

>  John Mallinckrodt writes:
>
> > ...
>
> But Jay...  Here's a typical problem to solve:  
>
> 	 An insulated liter container with 0.09 kg of water is shaken
> 	by rapidly raising and then lowering the container 1 meter. 
> 	 Assume that all of the motion energy raises the temperature 
> 	of the water 0.5 K.
>
> 	What would be the minimum number of shakes required?
> 	
> 	
> Why is it easier to souve such problems using calories rather than
> joules?  

Well Aich ... ;-)  I don't see why we'd need to use any unit of energy at
all in this problem and, even if we did, I certainly don't see any
advantage to one over any other.  Are you implying there *is* some such
advantage?  Otherwise, why do you ask?  After all, I'm not the one arguing
that we abandon the use of a perfectly good and often useful unit of
energy. 

John

P.S.  I suspect the answer that you are looking for is 

   c_water * DT     (4186 m^2 s^-2 K^-1)*(.5 K)
   ------------  =  ------------------------  =  214
       H * g         (1 m)(9.8 m s^-2)

but I don't place a lot of faith in this calculation because the real
answer will depend far too significantly--and is possibly much higher,
possibly much lower--depending upon just how "rapidly" you raise and lower
the container. 

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