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# Thread: What is the weight of our moon?

1. Originally Posted by marco
While I'm on the subject of weight. Why do we say we weigh X kg on a scale and not Newtons? My scale says I weigh 82 kg but I know it is 82 Newtons. Am I wrong?
W=mg

803.6 N

Give or take...

The reason why it's confusing is because mass is a scalar while weight is a vector. It can be represented in grams but a scale does actually measure weight rather than mass. Try standing on a scale in a weightless environment, freefall in a vacuum or in orbit.

This is why we can say you weigh less on the moon. Though your mass still stay the same.

This is a very important thing to know when engineering something like a roller coaster or when even considering what scientists mean by the higgs being responsible for mass. Weight is not mass but because humans use earths gravitational acceleration's forces while standing still you can consider it as being accelerated upwards. Hence the formula F=ma is rewritten as W=mg.

Another reason why it's confusing is when people round off g as being 10 rather than 9.8. Then 82kg will be 820N which is a problem cause even though g is designed as a constant it's not exactly the same everywhere on earth.

Here's a image showing the slight gravitational differences on earth's surface:

Which is also not perfect cause tides and such also changes the amount of matter under your feat.

2. Seems like mass and weight is used intermittently as the same thing. To be correct in my view a scale should show Newtons and not Kg.
Newtons includes gravity where KG is the mass without gravity.

Mass was not really understood and even after when the Higgs Field was found in 2012 to be the culprit to excite the up down quorks to add energy to them did they almost understand why matter had mass. Energy is after all directly proportional to mass. So energy is mass. Confusing I know but real.

3. Originally Posted by marco
Seems like mass and weight is used intermittently as the same thing. To be correct in my view a scale should show Newtons and not Kg.
Newtons includes gravity where KG is the mass without gravity.

Mass was not really understood and even after when the Higgs Field was found in 2012 to be the culprit to excite the up down quorks to add energy to them did they almost understand why matter had mass. Energy is after all directly proportional to mass. So energy is mass. Confusing I know but real.
Perhaps you should be less excited about being corrected on your thread, and then just use basic grammar?

Edit: I think you meant "interchangeably"?

4. Been away for some time studying English grammer but still have difficulty with speling.

We measure force in the unit known as a newton. So your scale should display your weight in newtons. However it will normally indicate your weight in kilograms. But kilograms is actually a measure of your mass and this is where the confusion starts.

It will be more correct if the scale shows KGF. (kilogram force).

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