let's talk about energy specifically the different kinds of energy that are out there the first one that we're going to talk about is kinetic energy any object that is moving has kinetic energy so for instance let's say if we have a block that is sliding across a horizontal surface if that block has some kind of speed attached to it it has kinetic energy kinetic energy is proportional to the mass of an object and the square of the speed of that object now some objects have the ability to rotate so think of a will that's spinning in this case it has rotational kinetic energy now another type of energy is potential energy this is a type of stored energy as opposed to objects in motion a good example is let's say if we have a ball or rather a block on this hill this block has the ability to slide down when it's sliding down it's going to have kinetic energy but if it remains at rest at that position it has the ability to fall or let's say if we put a ball above ground level that ball has the ability to fall so it has stored potential energy potential energy has to do with the position of one object relative to another so to illustrate this let's say this is let me draw a better picture let's say this is the Earth and let's say this is object one and object two both of these objects are above ground level and they have the ability to fall so they both have potential energy now which of these two objects have more potential energy number one and number two number two has a greater amount of gravitational potential energy because it's at a higher position so when it falls by the time it hits the Earth or it hits the ground it's going to be moving at a higher speed compared to object one if we neglect air resistance gravitational potential energy is equal to the mass times the gravitational acceleration times the height so as we increase the height of the object the gravitational potential energy increases so because object 2 is at a higher position than object one it's going to have a higher potential energy so this object wants to move from a high position to a low position as it does so energy will be converted from potential to kinetic now notice that the gravitational force is directed downward when an object when it moves in the same direction as the force that gives its potential energy that potential energy is going to decrease now if we were to move this object opposite to the gravitational force the potential energy will increase if we were to move the object in the direction of the gravitational force the potential energy will decrease I'm going to talk about that concept throughout this video as it relates to other forms of energy but remember this so in this situation we have a gravitational field if you were to move the object opposite to the direction of the gravitational force the potential energy is going to go up if you were to move it in the direction of the gravitational force the potential energy will go down now this situation is similar to another type of potential energy called electric potential energy in which case the potential energy is determined by the relative positions of charged particles so let's say we have a charge plate a positively charged plate and we have two charges we'll call this charge number one and charge number two looking at these two charges let's say they have the same magnitude of charge which one will have a higher electric potential energy charge one or charge two what would you say both of these charges will feel an electric force that's going to propel them away from the charge plate now charge one is closer to this plate so it's going to have a higher electric potential charge 2 is further away from it so it's going to have a lower electric potential if we were to move charge to opposite to the direction of the electric force if we were to bring it closer to the charge plate the gravitational potential energy not gravitational but the electric potential energy will increase because we're moving it in the direction opposite to the electric force now if we were to move the charge in the direction of the electric force the electric potential energy will decrease much in the same case as the gravitational potential energy in the last example so you can see the similarities here so electric potential energy and gravitational potential energy they're very similar if you look at the formulas for gravitational potential energy it's MGH and if you compare that to the formula for electric potential energy it's negative Q that's the charge times the electric field times the height or the distance between the charge and the charge plate so looking at these two formulas you can see the similarities instead of mass here we have charge instead of gravitational acceleration here we have the electric field and these two are similar h and y they're both basically distance but in a vertical Direction now there are other different types of potential energy the next one is the elastic potential energy this is commonly associated with Springs so let's say we have a spring whose Natural Life goes up to this point now if we were to apply a force on this spring to compress it we're going to transfer energy to the spring in fact that's what a force can do whenever a force is applied to an object it's transferring energy to that object so as you apply a force to compress the spring we're storing up potential energy in this spring let's call this situation A and situation B which one has more stored elastic potential energy situation A or B the more we compress the spring the greater the amount of stored energy in that spring will be so the answer will be situation B the potential energy stored in the spring is equal to one-half k x squared K is a spring constant with the unit's Newtons per meter so a spring constant of 400 newtons per meter tells us that in order to compress the spring by one meter we need to apply a force of 400 newtons this is the distance between the original natural length of the spring and the amount by which we compress it or by which we stretch it so if you stretch the spring that spring will also have stored potential energy the same as if you compress it so that's another way in which we could store energy we can store it in the form of a spring we can store energy by moving an object to a high position and we could store it by moving charges from one position to another so going back to this scenario if we were to move the charge if we were to apply a force and move the charge to a position that's closer to the positively charged plate we're storing energy we're increasing the electric potential energy of this charge if we were to move that positive charge away from the positively charged plate we're decreasing the potential energy of that charge and it naturally wants to move away from it now the reverse is true if we had a negative charge the negative charge wants to go closer to the positively charged plate so if we were to move it away from the positively charged plate we would be increasing its potential energy we're basically storing energy into the system the electric charge fills an electric force that wants to accelerate it towards the positively charged plate so if we were to move the charge opposite in the direction of that electric force we're increasing the electric potential energy of that charge so in other words we're storing energy in that system now there are other forms of potential energy another example is chemical potential energy so think of the energy that's stored in a battery that energy is stored in the form of chemical potential energy now once we connect this battery to a circuit let's say if we attach it to a light bulb we can release that chemical potential energy and convert it to light energy this will be converted to not only light energy but heat energy as well so electricity that is Flowing from this battery to the light bulb is the mechanism by which energy is transferred from the battery to the light bulb now there are other things that store chemical potential energy think about the foods that we eat think about rice beans chicken we derive energy from eating these foods which allows us to function to move to run to work out we talked about batteries already they can store chemical potential energy but even certain molecules like hydrocarbons think of the gasoline in an automobile we use gasoline to power our vehicles we use the internal combustion engine to convert the energy that's found in gasoline into mechanical energy which can drive the vehicle forward or we could use that mechanical energy to basically drive an alternator which will convert that mechanical energy into electricity which will charge the card battery so chemical potential energy is something that we tend to make use of a lot in our daily living now there are other forms of potential energy that is found in nature a good example has to do with a phase change so let's say we have a liquid and here are the molecules in this liquid when the liquid freezes into a solid something happens the molecules in a solid not for all solids but in the case of most solids the molecules tend to be closer to each other compared to a liquid and so when you freeze a liquid you're bringing the molecules closer together in most cases water is an exception and a lot of times when you do this energy is released particularly heat energy now a phase change occurs without a change in temperature so let's say we have this liquid at 45 degrees Celsius let's say that is the melting point of the liquid it can freeze at that same temperature so this is a form of potential energy that energy can be released without a change in temperature as the molecules or the atoms move closer together and as they freeze from a liquid to a solid that's an exothermic process energy is released Think About Steam when steam condenses into liquid water energy is released and this could happen without a temperature change steam at 100 degrees Celsius when it condenses to liquid water at 100 degrees Celsius it's going to release Heat so that's a form of stored energy that is in the molecules of steam the reverse is also true let's say if you were to release water in let's say a very hot and dry environment that water is going to evaporate evaporation has a cooling effect it's endothermic and so when water evaporates in a very hot dry environment it's going to absorb the heat in that hot dry environment cooling it down this is known as evaporative cooling so molecules the position of one molecule relative to another has potential energy as we see here in the case of a typical liquid as the atoms get closer to each other converting the liquid into a solid energy is released so this is a form of positional potential energy where the potential energy is based on a relative position of the atoms with respect to each other another example of this has to do with pressure so imagine if we have a container with gas pressurized gas let's say at 100 ATM that's atmospheric pressure and outside of that we have normal atmospheric pressure of One ATM so here we have a region of high pressure in the inside on the outside we have a region of low pressure now the gas particles in this container they're going to be very close to each other because they're forced into a region a small region of space and so when you force gas molecules into a small region of space the pressure is going to go up outside of that the pressure is low so the gas particles they're more spread out so in this situation now for gases and liquids the situation is different in this case we're dealing with a gas when the atoms are closer together you have more potential energy compared to when the atoms are further apart so here we have a situation of high pressure and high potential energy once we open this valve and we release the stored gas molecules the gas particles they're going to force their way into this opening and as they do so they're going to exert a force on this object as they exert a force on that object they're going to do work on it and so this system has stored potential energy because once we released it work can be done by this pressurized gas as the gas particles move from a situation where the atoms are close to each other to a situation where the atoms are further apart energy is released so if we want to store energy in the form of pressure we need to apply a force against the direction in which those gas particles want to go so if we were to take a pump and we were to force the gas particles into the small container increasing the pressure we're basically increasing the internal energy of the system but once we release that gas and let it flow in the direction from high pressure to low pressure energy is going to be released if you notice things tend to flow in that order energy likes to flow from a high position to a low position so like these gas particles the gas wants to flow from a region of high pressure to a region of low pressure in the case of this object it wants to fall from a position a high position to a low position even electricity let's say if we were to have a resistor and at this point we have an electric potential a positive 50. and here we have an electric potential of 10 volts positive 10 volts conventional current once the flow in the direction of high electric potential to low electric potential just as water wants to flow from a high position to a low position now the same is true with heat let's say if we have a region of high temperature let's say this is this object is hot it's at 100 degrees Celsius and this part is cold let's say it's at 10 degrees Celsius so here we have a region of high thermal energy here we have a region of low thermal energy heat is going to flow from hot to cold heat is the flow of thermal energy and that's usually how energy will typically flow it usually flows from something High to something low now you might be wondering what exactly is thermal energy when you're dealing with solids the thermal energy inside a solid has to do with the vibrational energy of those molecules if you were to increase the temperature of the solid those atoms in that solid they're going to vibrate more the vibrational energy is going to increase when you're dealing with gases the situation is a bit different because gas is their free to move so if you were to increase the temperature of a gas the gas particles they're going to be moving faster you're going to increase the kinetic energy of those gas particles and as a formula for this when dealing with gases the average kinetic energy is equal to 3 over 2 times Boltzmann's constant times the temperature so if you were to increase the temperature of the gas you're increasing the thermal energy of that system and you're also going to increase the kinetic energy of those individual gas particles which means those gas particles are going to be moving faster there's something called the root mean Square velocity of a gas particle and it's equal to the square root of 3 RT over M where T is the temperature that means the molar mass So Heavy Gas Mark heavy gas particles they tend to move slower but a gas particle or a sample of gas at higher temperature will have gas particles moving at a greater speed so when talking about the thermal energy of a solid typically you're talking about the vibrational energy of the molecules in that solid when you're discussing the thermal energy of a gas a lot of times you're talking about the speed at which those gas particles are moving because the hotter those gas that gas sample is the faster those gas particles will be moving the more average kinetic energy they will have now the next thing we're going to talk about is wind energy now wind even though you could use wind to basically generate electricity in the case of let's say if you have like a windmill or a wind turbine wind is more of a force so wind is basically like the force that pushes air molecules from one place to another but anytime you have a force you can derive energy from that because forces whenever they act on an object they can transfer energy to that object so energy can be derived from wind but we can't really say wind is an energy when it's really a force the next thing we're going to talk about has to do with light energy actually before we talk about light energy let's talk about Sound Energy now sound is a wave more specifically it's a pressure wave so let's say you have a speaker and it emits a sound what's really happening is you have regions of compression and expansion in the gas particles in the air so in one area the gas particles are very close to each other so this is a region of high pressure this is a region of compression after that the gas particles are more spread out that's a region of low pressure so that's a region of expansion and follow an expansion you have compression and so in a sound wave you have this alternating pattern of pressure you have regions of high pressure followed by regions of low pressure so sound is a wave more specifically it's a pressure wave so here's the region of high pressure and then here you have region of low pressure and then high pressure and so forth now a wave is basically a disturbance that can travel through a medium like water or it could travel through air or it can even travel through empty space so a wave is basically a disturbance that can transfer energy from one region to another but when dealing with sound sound doesn't really transmit through empty space it could be transmitted through air or it can be transmitted through a solid or even a liquid for instance let's say if a train is coming likely you can hear the vibrations on the ground you can hear the sound traveling through the ground sound can also travel through water think of sonar just as they can travel through air but an empty space you don't have a lot of particles where you can have regions of compression and expansion so sound really isn't travel in space but nevertheless sound is a wave and waves can transmit energy so that's what sound is it's basically a pressure wave now we also have light energy like sound light is a wave as well and as a result it can transfer energy so think about the light that we receive from the Sun because of that we can get electricity from the Sun let's say if we have a solar cell let's say we lay it out in the sun that solar cell will convert light energy into electricity and we could store that electricity in a battery let's say if we have a tree trees can also store light energy in the form of chemical potential energy going back to the first example this solar Style will absorb light energy and convert it to electricity as the electricity flows into the battery that battery is converting the electric energy into chemical potential energy in the case of a tree the tree can convert light energy into chemical potential energy by means of a process known as photosynthesis in photosynthesis the leaves of the trees will absorb carbon dioxide from the air and they're going to pull up water through the roots they're going to pull up water from their ground through their roots in this reaction and use in light energy they will convert carbon dioxide and water into a sugar known as glucose and at the same time the trees will release oxygen in the air for us to breathe so this is photosynthesis the process of converting light energy into chemical potential energy in the form of a high energy hydrocarbon so light carries energy as we could see and light is basically a wave you could think of it as a particle too so light is associated with particles known as photons a photon can behave as a particle but it can also behave as a wave as well there's something called the particle wave Duality even electrons can do this too electrons can behave as particles but they can also behave as waves but when talking about light has an oscillating electric field but it also has an oscillating magnetic field which is perpendicular to the electric field so because of the oscillating electromagnetic fields light is an EM wave an electromagnetic wave now there are other types of electromagnetic waves other than light we have radio waves microwaves infrared radiation visible light ultraviolet rays x-rays and gamma rays and beyond that Cosmic race as it moves to the right the energy of these radiation or forms of radiation increases the frequency also goes up but the wavelength decreases so gamma rays has a shorter wavelength than radio waves going to the left the energy decreases radio waves have the lowest energy they have the lowest frequency but they have the longest wavelength so that's another type of energy that we can discuss now there's also mechanical energy when talking about mechanical energy it's the sum of kinetic energy and potential energy so an object in motion has mechanical energy an object that has the ability to fall let's say an object at high position also has mechanical energy