 All right everybody, it's Mr. Langdell here. I'm gonna talk to you about a little bit of physics And I'm joined by my most excellent Belgian friend, Montseur Huckely-Poyreau Who is one of my favorite detectives from the Agatha Christie detective novels And he's here because we're going to be doing some analyzing We're gonna be trying to figure out some graphical analysis work There's three types of graphs we're gonna deal with in physics 20 in unit 8. We're gonna deal with our distance versus time graph We've done a bit of those earlier in the unit already We're gonna deal with some velocity versus time graphs, and this is a little bit of a new one some acceleration versus time graphs And we're gonna look at five possible cases where we can have different types of motion That is pretty much gonna encompass everything that you could come up against. I think in physics 20 So let's take a look at the first case first case. No movement This is when something is standing still now. What's the distance time graph for that gonna look like well? Pretty simply put it's a nice horizontal line The displacement is not changing. So if this is something like 10 meters It means that that object is staying at 10 meters and it's not moving anywhere. So What is your velocity time graph look like for that? Well, it's pretty simple really it doesn't look like anything because if you are not moving you don't have a velocity so you have no velocity time graph and Ditto for the acceleration. I mean if you don't have any velocity, you don't have any change in velocity So you don't have any acceleration remember no movement still counts as uniform motion because the motion is uniform the velocity of 0 stays the same Okay, we've dealt with that a little bit already. That's not too bad. Let's look at case 2 constant velocity and you notice I've got a positive sign here because I'm gonna talk about velocity in the positive direction So, you know that could be to the right or that could be To the east or north or something like that So displacement versus time graph. What's this going to look like? Well, if it's a constant velocity We are going to have a straight line diagonal But straight and in this case because the displacement is increasing as time increases. We've got positive velocity What does that look like in a velocity time graph? Well, it's going to be Again a horizontal line kind of like our displacement time graph was in the last example The difference here is in order to figure out whatever point this is going to be at maybe this is five meters per second How do we know that it's five meters per second? I'm looking at this graph. Well, what we'd have to do is pick two points off the line We'd have to find the slope the slope of our distance time graph is going to tell us what the velocity of the velocity time graph is What about our acceleration time graph? Well, take a look acceleration is a change in velocity Do you see any change? Poirot, do you see any change? He doesn't see any change. So there is no graph here. There's no acceleration time graph Remember one of the most important ideas here When you find the slope of a distance or it could be a displacement time graph, you're going to get velocity All right, that's not too bad. Let's look at case three in case three We're dealing with constant velocity, but in the negative direction. So what does that look like? There's our distance time graph looks a little like that Still straight, but downhill now. Here's our velocity time graph still horizontal But notice it's at something like maybe negative 10 meters per second. It's below the x-axis You guessed it If there's no Change in velocity there can't be an acceleration time graph And of course we could find the slope of our distance time graph and that slope again Would be exactly the same as the velocity we need for our velocity time graph Case four, what about a constant acceleration? What if we have accelerated motion? Well, as we looked at in the lesson on acceleration if this is a positive acceleration We're going to get a curve that looks like this Now what can we do with this equation? What can we or what can we do with this graph rather? Well, we can do a couple of things we can figure out velocities at different points By working out a tangent if we want found the slope of that tangent That slope will give us velocities if we did this two or three times or really as many times as you wanted to You could get a bunch of velocities that you could then go and plot and what you would get is a nice diagonal straight line so we go from curved to diagonal Now what's the acceleration going to be we'll take a look our velocity is increasing in a regular rate as our time increases So now we're going to have an acceleration time graph. It's going to be nice and horizontal So the pattern is curved diagonal Horizontal you're going to see that come up a lot And again, how do we find our acceleration time graph? Like how do we know what this point is if this was 7.5 meters per second squared How would we know that from our velocity time graph you take two points from our velocity time graph? We find the slope the slope of her velocity time graph is going to be the same as the acceleration and the acceleration time graph Again, so important. This is the analyzing the graph from the graphical analysis We find some information from one graph. We can use it to build another graph Okay, I said there's gonna be four five cases. So here's the last one. What about a negative? Constant acceleration well, that means we're gonna slow it down. So I don't know why don't we start? Why don't we start backwards and work our way back? So negative acceleration here. It is below the x-axis or the T-axis I guess for time What about our velocity time graph? Well, that's going to be going like this Okay, slowing slowing slowing slowing down And our Displacement time graph is going to be curved looking like that again going from curved to diagonal to below the x-axis So hopefully that gives you a bit of an idea of what some of these graphs mean How can we take one graph and turn it into another one? And so just by following some of these tips and using a bit of thinking you can figure out what a lot of graphs are talking about Hope that helps and if you have any questions make sure you check out the section of notes on the website graphical analysis