Do I weigh 50 kg or 50 * 9.8 kg?

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Discussion Overview

The discussion revolves around the distinction between weight and mass, particularly in the context of measurements taken on Earth versus other celestial bodies. Participants explore the implications of using kilograms as a unit for weight and the differences in weight experienced in varying gravitational fields.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that their weight is typically shown as 50 kg but questions the validity of this since kilograms are not a unit of force.
  • Another participant clarifies that on Earth, mass is 50 kg and weight is 490 Newtons, while also mentioning that scales are calibrated for Earth and display mass in kilograms for user familiarity.
  • A different participant humorously suggests stating weight in kilonewtons (0.5 kN) instead of Newtons.
  • One post discusses a method to confirm whether a scale measures weight or mass by applying additional force and observing the scale's response.
  • Another participant humorously states their weight as 21 Newtons on Ceres, indicating the variation in weight due to different gravitational forces.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate units for weight and mass, with some agreeing on the definitions while others highlight the confusion surrounding the use of kilograms for weight. The discussion remains unresolved regarding the implications of these measurements across different environments.

Contextual Notes

There are assumptions about the understanding of weight versus mass, and the discussion does not resolve the potential confusion regarding the use of scales and their calibration for different gravitational contexts.

Phys12
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When I take my weight, it often shows around 50 kg. However, in my Astronomy class currently, it was mentioned that an average person's mass is roughly around 50 kg.

So, which one of them is correct? It doesn't make sense for my weight to be 50 kg because kg isn't exactly a unit of force, but then do I really weigh 490 N? (I'm so fat!)

Thanks!
 
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On Earth your mass is 50kg and your weight (the force you exert on the ground) is 490 Newtons.

On the moon your mass would still be 50kg but your weight would be 81 Newtons because gravity is lower.

Most weighing scales (unsurprisingly) measure weight not mass but because they are intended for use on the Earth only they are marked in Kg because that's what people are familiar with. They won't work correctly on the moon.
 
Phys12 said:
(I'm so fat!)
Just say you weigh .5 kN.
 
http://www.learnwithmac.com/2015/03/27/what-do-scales-measure/

..how do you know that your scale is actually reading force [weight] and not mass? Well there is an easy way to confirm this. Stand on your scale close to a fixed object and then carefully push yourself down on the scale using the fixed object as a support. You will suddenly see the scale reading increasing, indicating that your mass has increased. However this is not the case since you haven’t suddenly put on mass.
 
I only weigh 21 Newtons**(on Ceres)
 
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