## Weighing yourself on a solid surface vs carpet

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?

 Why don't you try it and tell us what your results are?
 Recognitions: Gold Member Science Advisor Staff Emeritus 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.

## Weighing yourself on a solid surface vs carpet

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.

Mentor
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.

 Pendergast found that digital scales were far less prone to the effect because of a slight difference in their internal mechanism.
That is an important statement.

Quote by 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.

 Pendergast found that digital scales were far less prone to the effect because of a slight difference in their internal mechanism.
That is an important statement.
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.