# Linear relationship direct proportionality definition

### catchsomeair.us: physics coursework analysing direct proportion

A relationship is a way of describing how one variable can affect another. If a relationship is linear, then a change in one variable will cause a. Direct and inverse proportion. Proportion is used to show how quantities and amounts are related to each other. The amount that quantities change in relation to. Directly Proportional. THIS IS LEGACY linear graph, The points follow Things that are in direct proportion will produce a graph with an equation of the form.

This is, let me call this the Y over X column. I'm just gonna keep figuring out what this ratio is for each of these pairs. So for this first pair, when X is one, Y is one half, so this ratio is one half over one.

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Well one half over one is just the same thing as one half. When X is four, Y is two, this ratio is gonna be two over four, which is the same thing as one half.

When X is negative two and Y is negative one, this ratio is negative one over negative two, which is the same thing as one half. So for at least these three points that we've sampled from this relationship, it looks like the ratio between Y and X is always one half.

### Curve Fitting – The Physics Hypertextbook

In this case K would be one half, we could write Y over X is always equal to one half. Or at least for these three points that we've sampled, and we'll say, well, maybe it's always the case, for this relationship between X and Y, or if you wanted to write it another way, you could write that Y is equal to one half X.

Now let's graph this thing. Well, when X is one, Y is one half. When X is four, Y is two. When X is negative two, Y is negative one.

I didn't put the marker for negative one, it would be right about there. And so if we say these three points are sampled on the entire relationship, and the entire relationship is Y is equal to one half X, well the line that represents, or the set of all points that would represent the possible X-Y pairs, it would be a line. It would be a line that goes through the origin.

Because look, if X is zero, one half times zero is going to be equal to Y. And so let's think about some of the key characteristics.

## Direct and inverse proportion

One, it is a line. This is a line here.

It is a linear relationship. And it also goes through the origin. And it makes sense that it goes through an origin. Because in a proportional relationship, actually when you look over here, zero over zero, that's indeterminate form, and then that gets a little bit strange, but when you look at this right over here, well if X is zero and you multiply it by some constant, Y is going to need to be zero as well. So for any proportional relationship, if you're including when X equals zero, then Y would need to be equal to zero as well.

And so if you were to plot its graph, it would be a line that goes through the origin. And so this is a proportional relationship and its graph is represented by a line that goes through the origin.

Now let's look at this one over here, this one in blue. It is here written in lower case script. In this context it is shorthand for the phrase 'is directly proportional to.

Whenever you have a direct proportion as stated above you can change it into an equation by using a proportionality constant. Here is how the direct proportion would look as an equation: The above would read 'A equals k times B.

If two quantities, A and B, are directly proportional, then there is a proportionality constant, k, such that k times B will equal A. The graph of a direct proportion is a straight line through the origin. B will yield a straight line through the origin with k as the slope: So, if you graph data for two related quantities, and that graph yields a straight line through the origin, then you know that the two quantities are in direct proportion.

Examples of direct proportions abound in physics.

## Proportional relationships: graphs

For example, Newton's second law of motion states that the acceleration of an object is in direct proportion to the force on the object.

So, if you triple the force on an object, then the acceleration of that object will also triple. Of course, when you triple a quantity you are changing it by a factor of 3.

So just to 1. Notice, every time x is increasing by 1, y is increasing by 0. That's exactly what they told us here. Now, if x increases by 1 again to 5, then y is going to increase 0. And I like this point because this is nice and easy to graph.

So we see that the point 0, 0 and the point 5 comma 2 should be on this graph. And I could draw it. And I'm going to do it on the tool in a second as well. So it'll look something like this.

And notice the slope of this actual graph over here. Notice the slope of this actual graph. If our change in x is 5. So notice, here our change in x is 5. Our change in x is 5.

### What is linear relationship? definition and meaning - catchsomeair.us

You see that as well. When you go from 0 to 5, this change in x is 5. Change in x is equal to 5. What was our corresponding change in y? Well, our corresponding change in y when our change in x was 5, our change in y was equal to 2.