Mass in Physics

What is the Unit of Mass?

Mass has many different units, including pounds$\text{(lbs)}$, tons$\left(\text{T}\right)$, and grams$\left(\text{g}\right)$; however, the most widely used measurement for mass is the kilogram$\left(\mathrm{kg}\right)$. The kilogram is defined as the official unit of mass by the International System of Units, which defines the SI units. The kilogram is one of the seven base units that make up the rest of the SI units.

There has often been some confusion about mass; particularly, what is different between mass and weight. We said earlier that the more mass something has, the more force is needed to move it. Weight can be explained as a value that describes the force the gravitational pull of the Earth has on mass. At the same time, weight can also be described by the force any gravitational pull has on mass, meaning that if you were to go to a different planet, your mass would stay the same, but your weight would change! The weaker the gravitational pull of the planet or celestial body (such as the Moon), the less you would weigh if you were standing on it. This is why when astronauts were on the moon, they have to bounce along the surface, gravity isn’t pushing down on them as much.

The moon is smaller than Earth, so the gravitational pull is weaker, meaning your weight will be less there than it is here!Wikimedia Commons

We just mentioned that your mass would stay the same no matter which planet you were on. This is however true in all cases, the mass of any object or person will never change no matter what. This is known as the principle of Conservation of Mass. In more detailed terms, it also states that if an object were to be taken apart, the total mass of that object would be divided exactly within all of its parts, and if they were to be put together again, the sum of all of those parts would equal the mass of the initial object exactly.

Mass in action. We know that the yellow ball must have a higher mass than the blue ball, as it pushes down on the scale more so, due to the force of its weight.ScienceAlert

How Do We Solve a Calculation of Mass?

Mass has a few different ways to be calculated depending on the information that we have at our disposal. One of the primary equations we need to be concerned with is the following:

$m=\rho V$

Where$m$is the mass,$\rho$is the density, and$V$is the volume.

Density

Density defines how much of something there is inside a specific amount of space. Therefore, the denser something is, the heavier it is. For example, imagine we had a ton of feathers and a ton of steel. They both have the same mass, but steel is a lot denser than feathers, so that means that way more feathers are needed than steel to make up that ton. At the other end of the spectrum, volume is quite straightforward. Volume is used to define the amount of space something fills.

What is an Equation Example of Mass?

We’re now going to look at how this equation may be used in a few different circumstances with some examples, so you’ll know what to look out for and how to solve them: