Video transcription

Hi, I'm Brian with Today we are going to explore how scales work. Scales are a instrument that are used to measure the mass or weight of a substance. There's two major categories for scales. There's balances, and then there's spring scales. Let's take a look at what one of those look like and how they determine the mass or weight. Okay, so first we're going to start a balance. Balances are things that most of us are familiar with. We've seen them at one point or another. Basically, what you do is you have two different panes. They're on a single bar and it's balanced. It's balanced. You place your substance of unknown mass or weight in one of the sides and it makes it unbalanced. Then you add different weights of known quantity. So you know exactly how much you're adding to the other side. When it comes out level or equal you end up knowing the weight because you know exactly how much you added to balance it out. You can see that this definitely depends on having a balance that is well calibrated. The other type of scale or the other major type of scale are spring scales. These rely on the stretching or compressing of a spring of a known elasticity. You have your scale and something attached to it. Then in this example, we've added fruit to our bowl and it stretches our spring out. Since the spring has a known sort of elasticity constant. The people who made it know exactly how much that change should be worth. In turn, that change translates to the weight of the material. If you're looking to get really accurate measures, spring scales have two limitations to them. First of all, they don't take into account the variation and gravitational fields that occur locally. Maybe you didn't know, but gravity varies by location. That can affect the measurement by up to point five percent. So if your not looking to be too accurate, that shouldn't concern you. The other problem that spring scales sometimes have is depending on the temperature the elasticities of how much the spring will stretch or compress is slightly affected by the temperature. That could add a little bit of air to your reading as well. This has been a brief discussion of how scales work