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Re: Stop using calories?




John Mallinckrodt writes:

herbgottlieb@juno.com wrote:

But students learn that the calorie is a unit of HEAT ENERGY.
Isn't is possible to raise the temperature of 1 g ...... by shaking
the liquid or subjecting it to electromagnetic radiations?
Why use the term CALORIE at all if it is just as easy to raise
the temperature of 1g ..... with 4 joules of energy ....any kind
of energy?

John Mallinckrodt answered

I'm willing to avoid calories when and if it makes sense to, but I
don't follow this argument. It's not "just as easy;" it's the same
thing.
If we shake 90 grams of water and find that it's temperature rises by .5
K
it's certainly easier to calculate the work done on it in calories
than in joules.

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?

Herb Gottlieb from New York City
(Where shaking water does not get it very hot)