the first part of physics - I've summed it up by one word called thermodynamics it takes quite a bit of actual lecturing and problem-solving to understand what that really means but in a nutshell it all talks about heat energy and what happens to a system when we add heat to it and can we get the system to do any work for us we want to build things right we want to make a system like a engine or something do something for us so we want to calculate how to make it do work for us well it turns out that matter like think of a gas right matter it consists of atoms moving around a gas right that matter can contain energy right we talked about energy before that was motion things moving have energy well it turns out these gas molecules are moving everywhere so there's tons of energy inside of a of a collection of gas particles right we measure this energy as temperature right so we're gonna that's kind of the first thing we talked about we talked about temperature of for instance a gas being the average kinetic energy which is remember that energy of motion I haven't given you any equations yet but it's the average value of the kinetic energy of the gas molecules so there's a lot of energy in a gas and it turns out if I add heat to a gas like a flame or something then I'm gonna increase the motion of those particles and since the motion is the energy then I've increased the temperature which I can measure with a thermometer so you all know this this is simple stuff if I add it put a flame under water or gas its temperature is gonna increase because the motion of the atoms is increased and that's what the thermometer actually measures is the average value of that alright so what we really want to do when we talk about thermodynamics is we want to figure out if we can get any of the any of this heat energy to be converted into work so typically what we're going to start by doing is we're gonna look at a piston you can think of a car piston but really now I want you to think more of like a like a steam engine kind of thing so if I have a piston inside of a chamber down here very low to the bottom part here and now outside the other side of the piston is like the rod it kind of sticks up through here and inside of this little area between the piston is a gas so this is a gas and right now the gas is kind of smushed right there but it's the gas it has a certain temperature and has a certain you know yeah it's a certain temperature and a certain volume there right but what do you think is gonna happen and I know that you know the answer what do you think is gonna happen if I take this gas and I add heat to it in other words add heat which we actually call Q in physics heat you can look at the historical reasons why we call it Q but anyway we we call it Q which means adding heat energy what's gonna happen so you can kind of think of like a little candle being under here with like a little flame or something under it it's heating it up what's gonna happen well the gas is gonna get hotter and hotter and hotter which means it's moving more and more the gas particles are moving and they're gonna expand that piston so the Pistons not gonna be that low anymore the piston might rise and the piston might then be pushed up like this right and so this is going to be a larger volume of the same gas I haven't added any gas the gas is there I'm just making it get bigger by adding energy to it but notice what happens whenever I push the piston this thing moves up so we say that this is done work it does whoops does work W because I can connect this piston to anything I can connect it to a railroad well you know a train you know wheel at the side of a trainer I can connect it to an actual to get it to turn something to get a car to move inside of a jet engine there it is differently designed it's not a piston like this but it's the same kind of thing I'm changing the chemical energy of the fuel into a spinning motion and a turbine and I'm pushing it out of the back of the engine and I'm creating thrust so I'm generating work from basically heat energy or in the case of a jet engine chemical energy but it's the same sort of thing you're taking energy in and you're turning it into work coming out work is basically energy of motion of something doing something on the environment all right so this looks like you're getting something for nothing right like oh I'm doing work it's great but you're really not because I have to come up with a some place to get this heat from in this case I put a candle here so I have the energies coming from the candle wax and combusting the oxygen or in the jet engine it's the jet fuel combusting with the oxygen or in a rocket engine it's the hydrogen combusting with the oxygen rocket fuel right so I'm getting the energy from matter and then I'm turning it into some sort of useful work right but in terms of thermodynamics there's a couple of laws of thermodynamics the first law of thermodynamics I'm not going to go too deep into this because we're gonna have many many discussions about this but the first law of thermodynamics basically says you can't you can't get more work out of a system W then you put in as heat Q when it basically means is you can take some mechanism any mechanism you want add heat to the system and you'll get work out but you will never get more work out than you put in and that's basically why perpetual energy machines are impossible no one's ever invented one it is impossible in the universe that we live in to get energy or heat or work out of a system that is actually more than what we start off with whether it's chemical energy whether it's solar energy whether it's energy from a candle whether it's a nuclear energy whether it's any kind of energy we have any experience with whatever you put in you're gonna have some losses here because see the the piston the real life has friction you're gonna have real losses so you're never gonna get exactly the same amount of work out as you put in you're gonna get slightly less but you will never ever get more work out and that's that's the first law of thermodynamics is why it's so simple to state it but it's so complicated to wash into complicated but the problems can consume challenging even though the concept is simple and then we have the famous second law of thermodynamics second law of thermodynamics this is better illustrated by another drawing what this basically says in a nutshell is that if I just let any system just evolve or just continue doing what its its thing without any outside stimulus as time goes on all systems in the real world tend to have greater disorder over time and let me show you what I mean by that if I have a box here like this and I divide it in half so I have a like a cork like a stopper in the middle and on the left-hand side I have a gas which fills the whole container so this is a gas so it's at some temperature or whatever I don't have any flame or anything I just have a gas there and then what happens is I go and I have another state after I remove that cork what do you think is going to happen so here I have this here all of the gases on one side then I pop that thing out what's gonna happen you all know intuitively what's going to happen is yeah the gas will be over here but it will spread to completely and totally fill the other side of this container and it's gonna do that it's not really by magic it's because of the gas collisions happening all the atoms bouncing off of each other but you know that over time maybe it takes one minute maybe it takes 10 minutes but it's going to spontaneously expand to fill that larger volume and the reason it does that where I shouldn't say the reason but an observation is that this system has greater disorder in other words there are more places for the gas to be because it's a bigger space so gas can be here gas can be there gas can be here and they can all be moving at different speeds this this side has greater disorder this side has less disorder so what we say in physics is we say this has low entropy and we use the letter s to talk about entropy and this has high entropy or higher entropy yes so any system if you're just leave it alone it's gonna go from low in low entropy to high entropy and the way we talk about that math matically is Delta s I'll talk about that in a second it's gonna be greater than or equal to zero what this means in I'm not gonna break it all out here for you because we're gonna get into a whole lesson here but Delta s means how does s change when we go Delta this triangle means change it means literally that's what it means it means change so how does this thing change from s1 to s2 so it's like subtracting the esses and what you're gonna find is that this s is going to be bigger than this one so when you subtract them that change the Delta s2 minus s1 is going to be greater than equal to zero which just means that this s is bigger than this one now it means that it could potentially be zero but in real life that always increases this one has higher entropy higher s this one has lower so when you take high minus low you get a number bigger than zero that is true for every system that we've observed in our universe it has a fundamental thing about our universe that entropy disorder increases over time as time goes on if you take a cup of coffee and black coffee and you put a little bit of milk like a few drops of you know maybe a teaspoon of milk right in there or creamer right in the beginning the creamer might gently be kind of right where you dropped it but if you just watch it it's going to over time by itself kind of dispersed throughout the coffee so that it's a evenly mixed throughout the coffee so we say that the creamer in the beginning has a low disorder low entropy but as time goes on it gets to higher and higher entropy because the cream is spread out all over the place is more disorder all throughout that coffee so we're gonna talk quite a bit about the second law of thermodynamics as we go on and then the last main topic that we have in physics too is we talked about the concept of waves in general waves now you all have a pretty good understanding of waves I think because you've been to the beach before so we say that we have this idea of a wave you've seen it before you've seen water waves come to you and so you you have an intuitive understanding that there's an oscillation here right there's an oscillation it's up and down up and down this is an oscillation up and down but you also know that the wave is carrying energy because you stand in the ocean the wave hits you and it can knock you over so it's carrying energy from the deep ocean into the beach and it's knocking you over so the wave can carry energy and it can it can transmit energy in that direction so you can also see this with a rope right if I take a rope and I tie it to the wall or I get my friend to hold it and I'm got my I got the other end I can start oscillating it up and down and it's gonna start to propagate a long look at the rope and it's gonna hit my friends hand and if I shake it hard enough his hands gonna start wiggling because I'm taking energy from my hand transmitting it through a wave hitting my friend and so I can use this kind of wave to transmit energy but there's another kind of wave called a sound wave which is slightly different but the same idea there's air between me and you and that air when my vocal cords vibrate that air is vibrated and it's basically shaking and it's oscillating it's a little different than this one a sound wave is like if you kind of think of a column of air between me and you if you just think of like a little column then what's gonna happen when I talk essentially is it's there's going to be a high concentration a high pressure of atoms and then less here and then there'll be another high concentration over here and then maybe less over here and then the process will repeat itself so this is called a compression wave where when I talk I'm literally moving back and forth and I'm compressing the air right in front of my mouth and that Trant travels forward towards you and carries energy with it and so if you could slice the air and look at it in cross-section you would see these high pressure regions of air that's where I've compressed the air and then I've had these lower pressure regions in the middle and but this whole thing this these these little regions are moving and they're carrying energy it's called a compression way this is actually called a transverse way we're gonna talk a lot about that but you have a whole lot of topics with sound waves in terms of Doppler shifting and frequency and amplitude all that stuff we're going to talk about so now we've basically talked about general concepts of physics 1 and physics 2 and next we're going to talk about the concepts associated with physics 3