Final answer:
Bathroom scales measure weight but show readings in mass units by dividing the weight force by Earth's gravitational acceleration. The scale reading changes if you push down on an adjacent object because you're applying less force to the scale. On the Moon, the same scale would show different readings due to the lower gravity affecting the weight force.
Step-by-step explanation:
The student has inquired about the behavior and purpose of bathroom scales, specifically pertaining to their functionality when applied to measuring weight and mass. A bathroom scale measures the weight of the object on it but provides the reading in mass units.
This is because weight, which is a force due to gravity, is expressed in Newtons (or pounds) and by dividing this force in most countries by the acceleration due to gravity on Earth (9.80 m/s2), the scale can provide the mass in kilograms.
When you stand on the scale, springs within the scale compress, and the amount of compression corresponds to the downward force you are exerting on the scale. If you were to push down on a nearby table while standing on a scale, the reading would decrease because you are exerting part of your force on the table instead of the scale.
Lastly, the same scale would not measure the same mass on the Moon as on Earth because the Moon's gravity is only about 1/6th of Earth's gravity, meaning the force exerted would be less and hence the scale would show a lower mass reading.
Mass vs. Weight
It is essential to note that mass is a measure of the amount of matter in an object and is constant regardless of location, whereas weight is the gravitational force acting on that mass. Therefore, while a scale measures the weight, it must be calibrated differently in a different gravitational environment such as the Moon to reflect the correct mass.