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. It can only be used to measure weight (NB 
deliberate use of "weight", not "mass" not "force", but "weight". 
A spring, like your tug of war rope, requires a force at both 
ends to expand, or contract.