hi there my name is Kaylee today we’ll
be doing a physics lesson on conservation and types of energy so what
is energy we hear about it all the time people not having enough energy or
energy costing a lot of money but what really is energy energy is the ability
to do work something like jumping or running uses
energy the Sun gives off energy even driving a car takes energy but there’s
something really special about energy it can never be created or destroyed ever
not in the history or the future of the world the same amount always exists and
that can be a little confusing but energy can never be created or destroyed
it can be transferred so you can think of energy like a river it’s always
flowing and moving dirt rock grass fish and sometimes it move slowly and
sometimes water may even stop and pool and other water may move even faster and
create Rapids the two main energy types we will focus on are kinetic and
potential energy and in terms of energy and physics these are like opposites of
each other so kinetic energy is the energy of something moving and it
depends on two important things the mass or how heavy the thing moving is and the
velocity or how fast the thing is moving at and potential energy is the energy of
something at rest that’s high off of the ground or off of your zero point and it
depends on two things mass how heavy the thing at rest is and the height or how
high off of the ground the thing is so this is our energy checklist
we need mass and height for potential energy we need mass and velocity for
kinetic energy and if something has mass height and velocity you can have both
types of energies and that’s when you’re seeing the transfer or the flow like the
river of energy in real time let’s use a skateboarder at rest at the top of the
ramp as an example right now what kind of
energy does the skateboarder have well we know that she has mass because we
know that she exists and does she have height yes she looks very high off the
ground to me but does she have velocity what we said in the beginning that she’s
at rest so we know she’s not moving she has no velocity so if she does have mass
and she does have height but she doesn’t have velocity that means that she only
has potential energy right if we use our energy checklist mass height now let’s
say she’s gone half way down the ramp so right now what kind of energy does a
skateboard have does she have mass yes we already know she has mass does she
have height well she’s still pretty far off the ground so yes she has height and
does she have velocity well we know she’s rolling down the ramp so she’s
probably moving pretty fast so energy checklist yes for mass yes for
height yes for velocity that means she has potential energy and kinetic energy
both of them and she’s made it all the way to the bottom of the ramp and she’s
gonna be on her way up the other side of the ramp but right now at the bottom of
the ramp what kind of energy does a skateboarder have so from the checklist
yes we know that she has mass does she have height so right now at the bottom
of the ramp she’s the same level as the ground so no she does not have height
but we do know that she has velocity she’s still moving right she’s probably
going pretty fast down here at the bottom so yes she does have velocity
energy checklist yes to mass yes to velocity kinetic
energy it is so now we have the skateboarder and she’s in real time so
we can see what happens as she transfers her energy from potential to kinetic and
back again so I’m just going to explain the layout to you so here we have the
ramp here here we have the skateboarder that’s what we saw earlier in the video
and then here we have some tools that we’re going to use the first one is the
slide bar here you can see I can make the skateboarder smaller she has less
mass and larger she has more mass so I can change that leave her right in the
middle for now I can check this box for speed that gives me my speedometer so
I’m able to tell if how fast she’s moving if she has zero speed and how
that changes as she transfers energy and perhaps most importantly I’m gonna click
this bar graph and it’s gonna show me a little graph right here the only thing
I’m worried about is kinetic energy potential energy and total energy I’m
gonna pretend like this thermal energy here doesn’t count we don’t care about
it we’re not gonna worry about it so we’re just going to look at how kinetic
energy and potential energy transfer back and forth and if that changes the
total energy at all all right let’s play so let’s first start with potential
energy so let’s get our bar graph up there we’ll get our speedometer up there
just so that we will know when she has to go we know that she has mass here
from the slide bar let’s keep it right in the middle for now and let’s go put
her up high and see what happens all right so right here let’s look energy
checklist we know that she has mass we know that she’s very high off the ground
and let’s see potential energy here I see zero kinetic energy I have zero
speed that all makes sense so my total energy the only energy I have is
potential energy checklist let’s see what happens when I change the mass so if I give her less mass potential energy dropped a lot total
energy dropped the same amount because I only have potential energy and if I make
her way bigger potential energy got a lot bigger total energy got a lot bigger
and that’s just from changing the mass so we understand now that checklist mass
is important let’s put it right back in the middle and see now height so we kept
her up here let’s see what if we started her up here so she’s not moving still
zero kinetic energy is zero but looking at potential energy dropped a lot we
didn’t change the mass this time all we did was change how high off the ground
she is so that makes a lot of sense then potential energy will change based on
how high off the ground we are up high down low or it will change if I’m a
small object with not a lot of mass or if I’m a big object with a lot of mass
cool let’s write it right back in the middle let’s put her back up to the top
and now let’s give her some speed so we’re gonna get her going so we should
see the speedometer the red arm here is gonna go up and we should see kinetic
energy kick in and let’s see what happens to this potential energy bar as
the kinetic energy kicks in let’s see all right there it is do you see so I’m
getting speed I’m going back to zero getting speed going back to zero getting
speed Oh nice I’m gonna give it a pause right about now so let’s see what
happens we have speed we have mass so energy check those that means we do have
kinetic energy perfect and we have mass we know we have height so we know the
potential energy and our total energy here looks like it’s bigger than both of
these that means we have both energies right now we have kinetic energy because
we have mass and velocity and with potential energy because we have mass
and height off the ground so I’m going to change this to slow motion now so we
can really see how these energy bars change so I’m going to let her go
and there she goes so we see as we higher off the ground but
she grows kinetic energy gets lower speed is lower and let’s see what
happens as she was back towards the bottom she’s getting faster so look at
she’s way faster now our red arm is higher on the speedometer our kinetic
energy is higher and our potential energy is almost zero because we’re
almost at the ground nice so this makes it really clear about how energy
transfers our total energy right it can’t be created or destroyed it’s
always the same and it just transfers between kinetic energy and potential
energy so nice job the next thing that you should do is go watch the friction
and energy video and you’ll learn about how friction changes kinetic and
potential energy totals so check that out and remember to always be clever

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1. Aparna Srijith says:

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