Final answer:
Bathroom scales measure the weight that is transferred from your body and clothes to your feet and then to the scale. The scales provide a reading in kilograms by converting the weight, based on Earth's gravity, into a unit of mass. The scale wouldn't read the same on the Moon due to the differing gravitational pull there.
Step-by-step explanation:
When you step on a scale, the scale measures the weight or force due to gravity on the entire system of your body and your clothes. This is because the weight of your clothes is transferred through your body to your feet, and therefore to the scale. Bathroom scales contain springs that compress in proportion to the force exerted on them. The compression of these springs provides a measure of your weight (force in newtons or pounds), which is then converted to give a reading in kilograms, a unit of mass. This conversion is based on Earth’s gravity and assumes you are not accelerating.
If you stepped on the scale while in free fall, such as in an elevator with a snapped cable, the scale would not show your real weight or mass. During free fall, everything inside the elevator is accelerating at the same rate due to gravity, resulting in a temporary state of weightlessness until the fall is stopped by automatic brakes or other means.
Furthermore, the scale would not measure the same mass on the Moon as it does on Earth because the gravitational pull on the Moon is different than that of Earth. Your mass is consistent across these environments, but your weight, which the scale measures before conversion to mass, would be less on the Moon.