Weighing yourself on a solid surface vs carpet

fawk3s

Recently I started thinking about it, because apparently you get different results. At first, I thought you would weigh less on a carpet (according to the scale), because the carpet supports some of your and the scale's weigh. But thinking deeper into it, I actually figured it shouldnt make a difference, since the Earth's gravitational force is same in both cases and it doesnt really matter if the scale is supported entirely by the solid surface or the solid surface + the carpet, because they have to balance the same force anyway in order for the scale to remain still/not move.

So gaining interest in the subject, I started googling it, and to my surprise I found statements to both that "the scale shows you weigh more on a carpet" and "the scale shows you weigh less on a carpet than on a solid floor."
I also came across this interesting explanation, yet it only explains one version: http://www.newscientist.com/article/...d-surface.html

So Im a tad confused here. Does the result depend on the scale itself and the way it's designed/manufactured? (Because I can think of a couple of minor details which could give both results in scales.) Or is there a better explanation out there which supports one statement and crushes the other?

Thanks in advance

skeptic2

Why don't you try it and tell us what your results are?

HallsofIvy

I like Skeptic2's response but with a null result, you might argue that you scale is not accurate enough to measure the difference.

Fawk3s, have you learned that "F= ma"? As long as you have 0 acceleration (I started to say "motionless" but actual speed or velocity doesn't matter), the scale will record the same weight whether it is on a hard surface, or carpet, or a spring or whatever. The key is "0 acceleration". IF, as a result of placing the scale on a carpet (or spring or whatever) you had, momentarily, non-zero acceleration, then, at that instant, the scale would be off by "ma" where a is the acceleration.

dipole

The only difference the carpet makes is that the scale can shift around much easier on carpet, and this can potentially throw off the measurement quite a bit.

mfb

Two other possible effects I found:
- On a carpet, the scale might be tilted a bit, which increases internal friction as it is not designed for forces horizontal to its surface.
- You are always moving a bit, which leads to a variable force on the scale. On a solid surface, this directly changes the force the scale sees. On a carpet, you get some damping. Now, depending on the measurement concept, the scale might react differently in those cases.

That is an important statement.

fawk3s

I actually thought of that as well, and thats why I said I can see how it can both show that you are heavier and lighter. Im glad you pointed that out.
And I guess that statement pretty much does seal the deal indeed.

Thank you for the answers.