Ron Hitler Barrassi wrote:
> 
> 
> Ron Hitler Barrassi wrote:
> 
>>>> If that is the case, why did you suggest using a spring based device 
>>>> to measure the downward force 
>>>
>>>
>>>
>>>
>>> Because I have heard of Hooke's Law.
>>>
>>
>> But not the gravitional constant apparently.
>>
>>
>>>> when the correct way to measure force is it's effect on moving *a* 
>>>> body of mass?
>>>
>>>
>>>
>>>
>>> It's "effect"? I don't even know what that is supposed to mean. Who 
>>> says that a mass acted upon by a force must be in motion? Push 
>>> against a building as hard as you can. The building does not move, 
>>> but you are still exerting a force upon it.
>>
>>
>>
>> F=ma
>>
>> (I've highlighted the definite article to draw attention to your 
>> misreading)
>>
> 
> 
> I didn't elaborate on this point. You cannot use a spring to measure a 
> force. 

Really? Don't tell Hooke.

> It can only be used to measure weight (NB deliberate use of 
> "weight", not "mass" not "force", but "weight". 

Weight is a force.

> A spring, like your tug 
> of war rope, requires a force at both ends to expand, or contract.

Yes. In the case of a bathroom scale that measures weight with a spring, 
the person standing on the scale provides the force at one end. The 
floor beneath the scale provides the force at the other end.

- Kevin