Question

The two methods used for determining mass are:

measuring directly on a scale
measuring directly on a balance
measuring directly by displacement of water
calculated by measurements of w and g
@zepdrix @welshfella

Answer 1

measuring directly on a balance. One MASS balances another. I you know the mass of one then you''ve got it for the other. I think that this would work without modification on, say the moon, should you be able to get yourself and a laboratory balance up there.
With a spring balance though, you'd probably get a lower reading on the moon, because the WEIGHT of the mass would be less, due to moon's gravity being less than that of the earth, due to the moon's mass being less than that of the earth.
Of the other choices, I'd be tempted to go for the last one. The w you'd know by seeing it on the scale, the g you'd know by calibration with a known mass.
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