scott wrote:
>> So a force of 1N and a force of 1,000N both require the same amount of 
>> traction?
>>
>> How does *that* work?!
> 
> If the 1000 N force is on an object weighing 1000 kg, and the 1 N force 
> is on an object weighting 1 kg, then yes, they both require the same 
> amount of friction and will result in the same acceleration.

This must truly be the definition of "counter-intuitive". I cannot begin 
to imagine how this can be true. It is surely self-evident that applying 
a large force requires better grip than does applying a small force.

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>> If the 1000 N force is on an object weighing 1000 kg, and the 1 N force 
>> is on an object weighting 1 kg, then yes, they both require the same 
>> amount of friction and will result in the same acceleration.
>
> This must truly be the definition of "counter-intuitive". I cannot begin 
> to imagine how this can be true. It is surely self-evident that applying a 
> large force requires better grip than does applying a small force.

Not if the contact force is proportionally higher.

Press your thumb and finger together very lightly and see how much sideways 
force you need to slide them across each other.  Now press them together 
much harder and you'll find you need a much bigger sideways force to 
overcome the friction.

It's the same with a 1000 kg car and a 10 kg animal, because the car is 
pushing down on the road 100 times more than the animal it can generate 100 
times more forward force before slipping.

http://en.wikipedia.org/wiki/Friction

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>>> If the 1000 N force is on an object weighing 1000 kg, and the 1 N 
>>> force is on an object weighting 1 kg, then yes, they both require the 
>>> same amount of friction and will result in the same acceleration.
>>
>> This must truly be the definition of "counter-intuitive". I cannot 
>> begin to imagine how this can be true. It is surely self-evident that 
>> applying a large force requires better grip than does applying a small 
>> force.
> 
> Not if the contact force is proportionally higher.

I had assumed that the "amount of friction" already takes into account 
the contact force, along with the surface roughness, deformability and 
all the other things that affect friction.

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Stephen wrote:
> 
> Do you call that an argument? LOL

No, I call that a partly definition.

> From my memory of mechanics at school, hp was more an advertising unit ;)
> Bloody farmers couldn’t tell an erg from an egg :-)

Hp can be misleading, since it can mean lots of different hp's. It can
be either SAE or DIN and from the crankshaft or from the tires etc.

-Aero

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scott wrote:
>> So a force of 1N and a force of 1,000N both require the same amount of 
>> traction?
>>
>> How does *that* work?!
> 
> If the 1000 N force is on an object weighing 1000 kg, and the 1 N force 
> is on an object weighting 1 kg, then yes, they both require the same 
> amount of friction and will result in the same acceleration.

In other news, both feathers and hammers fall at the same speed in airless 
conditions.

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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Darren New wrote:

> In other news, both feathers and hammers fall at the same speed in 
> airless conditions.

Just once, I'd like to verify this experimentally...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Eero Ahonen wrote:
> Stephen wrote:
>> Do you call that an argument? LOL
> 
> No, I call that a partly definition.
> 

:D

>> From my memory of mechanics at school, hp was more an advertising unit ;)
>> Bloody farmers couldn’t tell an erg from an egg :-)
> 
> Hp can be misleading, since it can mean lots of different hp's. It can
> be either SAE or DIN and from the crankshaft or from the tires etc.
> 

Well I probably don’t think of hp as being anything as other than what 
non-technical people say. Who knows what work a horse can do nowadays? 
If the health and safety or animal welfare people allow it ;)

-- 

Best Regards,
	Stephen

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Orchid XP v8 wrote:
> Just once, I'd like to verify this experimentally...

http://www.youtube.com/watch?v=5C5_dOEyAfk

Of course, it wouldn't be *that* hard to do on earth.

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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>> Just once, I'd like to verify this experimentally...
> 
> http://www.youtube.com/watch?v=5C5_dOEyAfk

So much for "they did it on a soundstage and slowed it down". :-P

> Of course, it wouldn't be *that* hard to do on earth.

Yeah, because a high vacuum is easy to come by. Oh, wait...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Darren New wrote:
> Orchid XP v8 wrote:
>> Just once, I'd like to verify this experimentally...
> 
> http://www.youtube.com/watch?v=5C5_dOEyAfk
> 
> Of course, it wouldn't be *that* hard to do on earth.
> 

I've seen a demo of this in a few science museums.  It's pretty nifty, 
but in the vacuum they both fall fast enough that you don't really get 
to look at it for long.

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