Mass is the measure of the amount of matter. It is approximately the measure of the number of atoms in a given object. Mass is also the measure of an object’s resistance to gravity. The kilogram is the basic SI unit of mass.
Weight definition in physics
Weight is a force that is caused by the gravitational pull of the Earth toward its surface. The basic SI unit for weight is a newton.
*Weight and mass are the two that most often get confused with one another, but we will get back to that.
What is volume?
Volume is a measure of the amount of three-dimensional space that is being occupied by a liquid, solid, or a gas. The basic SI unit for volume is cubic meter (m³).
What is density?
Density refers to the measurements of how compact an object is.
Specific gravity definition
Specific gravity is in direct relationship with density. It is the ratio of an object’s density, and its contact substance. For example, if you want to place an object in water, the specific gravity would tell you if it would float or not.
Alright, we’ve just looked at the definition for each, but let’s go back through and see how they are related to one another.
How do they relate to each other?
So, we started with mass. For an object to have a weight, volume, density, or to find the specific gravity, it has to have mass. Or else we have nothing and this would all be pointless.
So, every object has mass. The next thing we would move to is the weight of an object. Every object with mass will also have weight, due to gravity from the Earth pulling that object toward its surface. In order to find the weight of an object, you would just multiply the mass of the object times gravity. Something else to keep in mind about weight and mass is that mass doesn’t change unless that object loses matter. However, the weight of an object with the same mass can change depending on where it is. Like the moon, for instance; if I go to the moon I will weigh less due to the lesser gravity, but I will still have the same mass.
Now, let’s move on to volume. We’ve already defined it. We’ve said that volume is the measure of space within an object. But how can we find volume? Well, all three-dimensional objects are going to have height, length, and depth. So, to find the amount of space within these three dimensions, we multiply those three dimensions together. The result will tell us the amount of space within that object.
Density is directly related to the mass and the volume. In fact, it tells us of the exact relationship between the two. To find an object’s density, we take its mass and divide it by its volume. If the mass has a large volume, but a small mass it would be said to have a low density.
This would let us know that an object’s matter is not very compact, but rather more spaced out.
If the object was low in volume but high in mass, then it would have a high density. This would tell us that the object’s matter is very compact within it.
This brings us to specific gravity. Again, specific gravity tells us the relationship between the density of an object and the contact substance. The contact substance is most often water. So, to find the specific gravity we would take the density of an object, and divide it by the density of water. If the specific gravity is greater than one, then we know that the object will sink. If the specific gravity is less than one, then we know that the object will float on water. This is because the density of water has to be greater than the density of the object.