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The many forms of and a couple of equations for energy energy can't be

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Energy, pretty important right you might not think too much about energy at least not [Woman appears in room]

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until you eat a big bowl of chili for lunch and an hour later you're nearly [Woman eating chili]

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comatose that's when you realize how much energy it takes just to get through

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the day and that's also when you realize that you should probably start eating [Woman sleeping]

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more salads where did that post lunch energy go did it just dissolve away nope

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in fact that's not possible energy can't be destroyed and it can't be created it

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can move from one place to another but it always has to be conserved like this

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espresso machine it's plugged into the wall drying electrical power and the [Woman points to espresso machine]

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machine converts out electricity into mechanical energy pumping water through

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the machine it also converts electricity into heat even if you want an iced latte

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it always starts off nice and hot and of course espresso machines generates down [Woman making iced latte]

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lots of sounds this home that haunts my dreams at night an energy conversion is

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also how solar panels work they're able to take light from the Sun and make it [Solar panels on a rooftop]

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into electricity and your body is able to take energy from caffeine and turn

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that into an eyelid that just will not stop twitching that's just an [Woman takes sip of coffee]

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occupational hazard in my line of work maybe I can just have another macchiato

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or three and never blink again problem solved there are lots of types of energy

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we've already talked about light heat electricity and sound oh and mechanical [Types of energy appear]

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energy along with kinetic it's easy to mix up mechanical energy and kinetic

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energy they both involve things moving after all kinetic energy is about motion

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in a direction forward or backward left or right up or down

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if it's moving then it's using kinetic energy mechanical energy is the ability

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for something to do work so it combines kinetic energy and potential energy

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there's also gravitational potential energy we also have nuclear energy which [Nuclear power plant appears]

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is really cool and really dangerous a little nuclear energy can go a long way

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an explosion this big can be created with only two pounds of uranium that's a [Explosion occurs]

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huge release of energy but energy can be released on a much smaller scale to ever

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pulled on a rubberband until it broke and snapped your hand [Girl pulls on rubber band]

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ouch pulling on the rubber band creates elastic potential energy and when it's

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released it converts into kinetic energy and maybe a welt on your finger too if

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you have a fridge at home you're probably familiar with magnetic energy [Pictures hanging on fridge]

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maybe mama still has one of your artistic masterpieces up there radiant

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energy is a property of electromagnetic waves including light that's how

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microwaves work you put your lunch in there and zap it the microwaves transfer [Girl places lunch into microwave]

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energy to the water molecules in your food and they get all excited and starts

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spinning around super fast like politicians but don't put them in a

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microwave that's ready to melt the skin off the inside of your mouth delicious [Girl eating lunch]

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energy is measured in joules and since it's always conserved any energy that

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goes into something has to equal the energy that comes out like we see in the

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espresso machine one type of energy can be converted into multiple different

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forms like on a roller coaster at the top of the highest hill all the energy [Woman sitting on a rollercoaster]

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is gravitational potential energy once the roller coaster starts heading down

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the hill picking up speed some of that potential energy gets converted to

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kinetic energy and when the coaster goes up into a loop some of that kinetic [Rollercoaster in a loop]

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energy turns back into potential energy one way we can keep track of all that is

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with a pie chart here's the chart for the coaster at the top all blue because

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it's all potential at the bottom of the hill it's all red and kinetic

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when we're upside down screaming our lungs out the chart is split whoa [Rollercoaster upside down]

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the pie chart isn't meant to be precise but it can help us think about how

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energy is changing in a system conservation of energy also lets us do

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some handy math stuff we know that everything we start with has to equal

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everything we end up with when energy is entirely converted from one form to

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another we can set the equations for each form of energy equal to each other

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say your I don't know bored out of your skull at work or school so you make a [Girl cleaning]

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paperclip spring and you make that spring sprawling all over the place

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because again BORED when you're dealing with a spring you're dealing [Spring jumps into the air]

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with potential energy but the energy for spring potential energy is different

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than the one for gravitational potential energy gravitational potential energy

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equals mass times gravity times height spring potential energy equals one-half

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K times x squared K is the spring constant which represents how stiff or

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stretchy the spring or elastic or whatever actually is in other words it's [Spring elongates]

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the springiness of the spring X is the symbol for the extension or compression

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of the spring which is measured in meters since X is for extension or

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compression we can think of it as displacement or how much you're moving [Spring compresses]

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one end of the spring from its original resting position and when the spring

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releases that potential energy its converted into kinetic energy and it [Girl holding sore eye]

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might also be converted into eye damage physics is risky folks the equation for

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kinetic energy looks like the spring potential energy equation kinetic energy

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equals one-half mass times velocity squared and because all the energy stays

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the same the potential energy prease broening equals the kinetic energy posts

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prong setting these equations equal to each other will come in pretty handy

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when we're trying to find a value for a variable while we're talking about

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elastic potential energy we should also point out how it relates to force in

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fact we get to look at a whole new force equation yes [New force equation appears]

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whoo-hoo sorry I should probably switch to decaf [Girl takes sip of coffee]

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the force applied to a spring equals the spring constant K times X which is the

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extension or a displacement of the spring we might also see this written

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with K as a negative that would just be the force the spring is applying as it [Springe recoils]

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tries to return to its regular state in other words the spring just wants to

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chill out and it starts getting forceful when we mess with it hold on is my [Man pushing spring in to a wall]

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spirit animal of spring whoa after my shifts done I hop on my bike and hope [Girl riding her bike home]

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the fresh air blows some of the coffee stink off me what kind of energy

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transfers happen on my trusty Schwinn and how are they different than the

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energy transfers in a car now bikes are pretty complicated

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you've got your pedals the chain the gears the brakes you might think you [Girl pedalling]

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just get on and start pumping your legs but there's more going on than that but

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we don't need to look at every little transformation of energy in this whole

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contraption we're looking big picture here but your legs are definitely

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involved so let's investigate them first what makes your legs move this is a [Anatomy of legs appear]

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biology class but I'm guessing you know what muscles are what's the source of

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energy that lets your muscles move and get the pedals turning now would be a

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burrito or soup or a hot pocket that's as hot as a surface as a Sun in other

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words food food has chemical energy in the form of calories our bodies use [Foods chemical energy amounts appear]

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those calories to fuel our muscles in a process known as magic

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like I said this is in biology class so we've got chemical energy in our legs

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and we apply that to the pedals the turning of the pedals makes all the

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mechanics of the bike work hey turning that definitely sounds rotational and [Girl pedaling her bike]

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sure enough we've got spinning and turning all over the place on this bike

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as a result of that energy the bike moves forward which now means we've got

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energy number three kinetic the bike moving forward is a classic case of [Girl riding bike down the road]

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kinetic energy and action so really if we think of the bike as one independent

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system mechanical energy is converted to kinetic energy and if we consider the

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rider part of the system our chemical energy is converted to rotational energy

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first now how about this gas go next to me this is in the Flintstone so [Car drives by girl riding bike]

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no muscle power is making the Beast move forward but it still wouldn't be going

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anywhere without chemical energy inside the motor gasoline is being burned which

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is a chemical reaction you can smell in the air but it's not constantly burned [Man with flame torch appears at gas station]

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like a bonfire we don't want to scare you but if you're driving a gas powered

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car there are hundreds of explosions going on under the hood every minute

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yeah riding a bike sounds even better now doesn't it the spark plugs in your

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engine fire off a spark that makes the gasoline explode it's a little tiny

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explosion but still boom that equation is what makes the Pistons on the energy [Engine in motion]

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move and the Pistons get everything in the energy spinning so we've got

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rotational energy all over again and of course the engine is connected to

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the drive shaft and the leg bones connected to the hip bone and the next [Car driving by]

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thing you know we've got kinetic energy to after all a car wouldn't be very

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useful if it didn't move a car also converts chemical energy into heat and

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sound as you know if you've ever said and your car gets hot enough that you [Man driving car down the road]

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can actually cook on it so yeah there's some thermal energy going on this [Chef cooking on car bonnet]

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happens with a bike too but to a much lesser extent try cooking something on

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your bike gears and you're just gonna end up with a cold mess so both systems [Girl riding alongside car]

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the bike and the car convert rotational energy into kinetic energy of course the

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bike riders provide the initial chemical energy which is why a twenty mile bike

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ride is way more tiring than a twenty mile car ride but cars are less [Man takes sip of soda while driving]

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efficient because more of their chemical energy is converted to heat and sound

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which don't actually help the car move that's a win for people power let's look

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at another scenario see we've got a ball that rolls down a ramp and comes to a [Ball rolls down a ramp into a spring]

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rest on a spring what equation represents the energy transfer and what

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would a pie-chart of the total energy look like okay so

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this isn't an everyday situation unless you happen to have a ramp with a spring

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at the bottom lying around but that's fine we can let our imagination lead us [Girl holding ball]

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down this ramp at the start when we're just holding the ball on the ramp all

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the energy involved is gravitational potential energy

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we'll make that yellow on our pie chart and the equation for gravitational

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potential energy is mass times gravity times height

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as the ball rolls down that potential energy gets converted to kinetic energy [Ball rolls down the ramp]

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how about we make kinetic energy a nice lavender on our chart halfway down the

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ramp and our pie chart is split right down the middle at the bottom of the

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ramp all that potential energy has converted to kinetic energy which equals

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one-half mass times velocity squared but when the ball comes to rest on the [Potential energy to kinetic energy equation appears]

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spring there's no more kinetic energy either in the end all the energy is now

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elastic potential energy which calls for let's say aquamarine

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so now our final energy equation shows the elastic potential energy equal to

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1/2 the spring constant times the displacement of the spring squared and

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that equals the gravitational potential energy that we started out with because

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all the energy has to be conserved there are different equations for different [Equations appear for forms of energy]

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forms of energy and we're not going to worry about those right now

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so long as we know that the general principle is the same you get out what

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you put in although I do want to mention the most famous energy equation of them [Einstein writes equation on board]

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all e equals MC squared yep Einstein's little miracle here is definitely in the

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top five best energy equations of all time and it means that we all have a

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huge amount of energy stored in the molecules and atoms that make up the goo

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that is the human body but after that bike ride and the caffeine wearing off [Girl takes seat on couch]

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I'm definitely not feeling like I'm storing any of that energy in me I think

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it's time to recharge the batteries with a nap energy is great to talk about in

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theory but when you have a post espresso crash that hole you can destroy energy [Girl drooling and sleeping on sofa]

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thing feels like a huge lie

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