*warning....possible detailed techno-geek stuff follows*
Iain Mannix wrote:
> Raising/lowering/front/rear.
>
> Byron Short once used a big hammer to convince me that raising one end
> of a car would make that end heavier. It is true.
In what way did his hammer convince you? 8-)
You can do it with
> two bathroom scales and a sawhorse(or anything that is relatively
> heavy that will not allow the mass to shift). Put two legs of the
> sawhorse on one scale, call it the front. Put two legs of the
> sawhorse on the other scale, call it the rear. Sit two
> bricks/dictionarys/heavy things on the sawhorses over the legs.
> Observe "front and rear" weight.
>
> Take the brick off the top of the sawhorse on the "front" scale, put
> the brick *under* the legs of the sawhorse, raising the "front" three
> inches(or however tall the brick is).
>
> There are still the same things on the scales - one sawhorse, two
> bricks - but the weight will change; not total weight, but
> distribution. It really works.
Ian, I respectfully suggest that this is an incorrect method of
demonstration. In one case, the scale is measuring roughly have the
weight of the sawhorse, and part of the weight of the bricks, because
the bricks load is shared by the sawhorse, and therefor distributed to
both scales. When you put the bricks under the sawhorse, the main change
comes from the one scale weighing 100% of the bricks, instead of have
the load shared.
I also disagree with the basic point, but I am willing to be shown in
what way I am wrong. It has always been my grasp, that in order to do
less work while appearing you are carrying the same load (hehe) when
carrying sofas or other heavy furniture, you should raise your end. The
higher end weighs less.
This seems simple when viewed simply. If one takes a long heavy object
and tilts it, eventually the higher end has almost no weight, and all
the wieght is on the lower end. Now a car is a little more different, in
that you didn't raise the entire car, you just changed it's location of
mass and center of gravity. The tires still rest on the ground. There is
also further complication because the higher end, though exhibiting
slightly less force downward, will be affecting by suspension changes
and the higher center of gravity.
In any case, I was pretty sure that raising one end of a bar lightens
it's load on that end. I did a quick test on a scale that confirms this.
The higher end of the bar weighed less when I raised it.
If I am missing something, please let me know what it is. I am not
trying to debate the point, just understand why something I have thought
for many years may be incorrect.
Respectfully,
Randy Chase
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