If the mass of Earth were to become half, how would you be able to measure your mass accurately, with spring weighing machines or balance scales?

If the mass of the Earth were to become half, the
acceleration due to gravity and consequently the downward force due to the Earth would
decrease. Devices that use springs to measure a person’s mass would fail to give the
correct result. This is due to the fact that these work on the principle that when a
spring is pushed or pulled by a force it compresses or stretches proportionate to the
force applied. Due to the difference in force exerted by gravity, the spring’s length
would no longer alter as it did earlier.

Balance scales on
the other hand will give you your correct mass. This is because the change in
acceleration due to gravity affects both your mass as well as the weight to the same
extent in relation to the unit you are being measured against, so the units will remain
the same. If 45 pieces were required earlier as a counterbalance for your weight, the
same 45 pieces will be required now.