A discrete mass distribution is made up of point masses arranged in fixed relative positions. To find the mass, centre of mass or moment of inertia you use summation. The density of such a body is non-uniform, it varies from place to place : it is infinite at the point masses and zero elsewhere.
Discrete mass distributions are hypothetical. They don't exist in the real world because point masses don't exist. All mass occupies a finite amount of volume. However, if the mass of an object is concentrated in regions which are small compared with the size of the object, then those regions could be treated as point masses.
Examples : a dumbbell/barbell is usually treated as two point masses at the ends of a massless rod; a simple pendulum is a point mass at one end of a massless string or rod.
A continuous mass distribution is spread out in space. Every point within the body is connected to the whole, there are no gaps. If the density is the same at all points within its boundaries it is uniform. To find the mass, centre of mass or moment of inertia of a continuous body you might have to use an integral, ie a summation of an infinite number of infinitesimally small parts in which the density is uniform. Integration is usually necessary if the density varies from one place in the body to another.
Examples : a solid sphere or cube, which usually have uniform density if made out of a single material such as wood or iron. The Earth and other planets have non-uniform density; they are more compressed towards the centre because of gravity.
An object can be a mixture of continuous and discrete mass distributions.
Answer from sammy gerbil on Stack ExchangeDoes continuous exist in real life?
What are good examples of discrete and continuous data?
Videos
Let's consider this experiment: a simple car accelerating from 0 to 100 km/h in 9 seconds.
->From a mathematical perspective, the car's speed must pass through each velocity between 0 and 100. So:
-> The car must be at each of the infinite number of speeds between 0 and 100. So:
-> The car must move through all of these infinite speeds in 9 seconds. So:
-> From a physics perspective we have "something", that moves infinite time in 9 seconds, so this "something" has infinite velocity (and is greater than C), and there is no physical thing that has bigger velocity than C.
Can you help me understand what I'm missing here?
(I believe that there is nothing continuous in life, everything is discrete.)
I recently watched a lesson about this and so many kids were confused. The teacher said sweets were discrete and also books. However, the students said you could have all sorts of sweet sizes if a sweet broke so wouldn't it be continuous. The same with ripped books that were still being used but the book is in two halves or 1/4 and 3/4 etc.
Even shoe size was quetioned as of places that customize shoes for you so you get a more accurate size and not the usual discrete shoe sizes that we are used to.
What I'm looking for is good examples for discrete data. I thought discrete could be living humans as I can only think of students saying you can be half dead which I could explain how that isn't really measurable.