Does Your Digital Scale Measure Mass, Weight, or Something Else?
Electronic balances are all over the place in a science lab. Yes, we even use them in physics. But here’s the fun part — do they actually measure mass? Oh sure, in the picture above it reads “103 g” and the “g” stands for grams. But is it really grams? Is that how it works?
Here’s what we can do. Let’s use a digital scale in some weird ways and see what happens. Don’t worry, I’m going to go over the important details about how a balance works at the end.
Mass vs. Weight
Let’s just get this out of the way. What’s the difference between mass and weight? Mass is a measure of how much “stuff” is in an object. Imagine that everything was made of LEGO blocks. Then the mass could be a count of the number of blocks in an object (not a perfect analogy). In reality, pretty much everything you see is actually made of protons, neutrons, and electrons. These are what make up the “mass” of an object. The units for mass are kilograms or grams.
When two objects with mass are near each other, there is a gravitational interaction between them to pull them together. This gravitational force depends on the masses of the two interacting objects and the distance between them. If you have a balloon on the surface of the Earth, there is a gravitational interaction between…
