On 31/07/2010 9:36 PM, Orchid XP v8 wrote:

> Yeah. It _is_ kind of conspicuous that all the examples talk about
> *lifting* an object. As if moving an object horizontally wouldn't
> require any energy or something...
>

That is because it is the simplest to describe. When you master this we 
will move on to friction on a horizontal plane then an inclined plane.

>> 1 Joule is also the energy transformed in heat in 1 second by a 1 Ohm
>> resistor when the current is 1 ampere.
>
> And here I was thinking that the heat produced depends on the
> characteristics of the material, not just the current...
>

The characteristics of the material is reflected in the resistance or 
vica versa.


>> What is the weight of your arm ?
>> What is its length ? (we have a couple to nullify to reach static)
>> (we assume so far the other joints of the arms are locked by the bones &
>> position, it might be different and might introduce more forces)
>
> Mmm, interesting.
>
> I guess ultimately, muscles generate forces. Presumably to hold an
> object still, the force generated by the total muscle system must be
> equal (and opposite to) the force of gravity. It's all quite
> complicated, since most forms of locomation involve levering, and you'd
> have to know muscle insertion points and pivot lengths and so on.
>
> I guess the really interesting question is, how much energy does it take
> for a muscle to produce a given amount of force? (And, perhaps more
> importantly, what variables does this depend on?)
>

You are getting there :-D

-- 

Best Regards,
	Stephen

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