What do scales actually tell us?

  1. Pengwuino

    Pengwuino 6,942
    Gold Member

    If you stand on a scale that says you're weight is 98kg, does that mean the scale is tellign you you weigh 98kg * m/sec^2? which inevitably means your mass is 10kg? (ok not using real world numbers here). It seems like scales weigh Force because in an elevator going down, your weight changes if your under an acceleration (and if you have ever put your arm on something while being weighed, you know your weight decreases).

    So actually, what im asking is if scale's #'s are fixed (divided by 9.8) to show mass instead of your weight
  2. jcsd
  3. Janus

    Janus 2,525
    Staff Emeritus
    Science Advisor
    Gold Member

    Actually it is measuring weight(force) in the gravitational MKS system. In this unit system the Kgf is the unit of force and is considered fundamental and mass is derived.
  4. robphy

    robphy 4,472
    Science Advisor
    Homework Helper
    Gold Member

    A scale measures the magnitude of the upward normal force it applies on you.
    In the english system, this force is measured in pounds (lbs).
    In the metric system, this force is measured in Newtons (N). However, possibly for psychological reasons, that force in Newtons is divided by 9.8m/s^2 and presented to you in kilograms (which would be your mass, as long as you use this scale on earth).
  5. Pengwuino

    Pengwuino 6,942
    Gold Member

    So it is divided by 9.8... thanks robphy.
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