things you make me do heroin for sixty
symbols right so this is an earth vortex
nitron let me get this right and this is
one of the top ten most wanted presents
for Christmas this year at least in the
UK so Brady being the cunning and shrewd
filmmaker that he is thought that for
Christmas it would be a good idea source
to make a film about this I just want to
point out that right at the start we are
not funded by nerf we don't get any
sponsorship no it looks a bit naff
particularly when you turn around you
know I must admit that as a child I
never got guns my parents never bought
me go on some you know when you look at
this you know it's early sort of techie
dress you always wear black like that oh
yeah and I walk around like this no you
know you've this grammar isin gone
culture instinct old culture that's that
this is the physics disc technology
where the discs gone so what this fires
out
are discs Norv discs but basically when
you look at this it's a mini frisbee and
the frisbee let's look at a tear John
let's look at it that way let's look at
it upside down so that's what that's
what we're fine on mini frisbees you
might argue well why why if something
that looks like a disc rather than a
pellet what's what's so special about
discs the great thing about frisbees is
I guess when we've seen these being
thrown I really wish I had a bigger
frisbee to demonstrate this where this
isn't going to work so well but when you
throw a frisbee you've got you've got to
think about that like any object that
you throw you got to think about the
aerodynamics go think about how does it
stay up in the air and - well a number
of key things is actually very very
complicated and complex the physics and
we can get 20 condo and pretty pretty
salivating I'll fire at brady right so
this is an opportunity i've longed for
for a long time oh I miss them nah
didn't sorry George
ah yes that's where I was hearing thank
you George
so these pellets are like like mini
frisbees so nerve disk technology as it
says on the box but basically it's just
a mini frisbee you can see it's just
like a scaled-down frisbee and the the
aerodynamics of frisbees is actually
quite complex and complicated because
you might argue away if they got that
ship well first of all it's got to stay
up in the air and so you've got to
generate lift somehow and this thing is
almost like a little miniature airplane
ring or an aerofoil and the key thing
here is that you've got to control the
velocity the speed of the air around
this thing and you've got to generate a
pressure difference and it's that
pressure difference that gives this
thing lift but in fact if you look at
this in quite a bit of detail although
you get lift if this thing was just
static if it was just if it was just
going through the air like that wasn't
spinning then in fact it would very
rapidly tip over and basically would be
very aerodynamically unstable great
thing about frisbees is that I wish I
could do this a bit better and spin it
on my finger a bit better when it's
spinning the important thing is spinning
is basically a generating angular
momentum and once it's spinning so it's
angular momentum is directed in one
direction and once if we're spinning in
that direction but this wonderful thing
called the right hand rule so the
spinning is in that direction the
angular momentum which is a vector
quantity so it's got a magnitude has
gotten a mind to and it's got a
direction it's pointing upwards
important thing is angular momenta is a
conserved quantity in physics so this
thing once you get it spinning in a
certain axis it wants to remain spinning
in that axis unless you generate a talk
via the air for example unless you've
got lots of wind but if you're working
with relatively calm conditions then
these things the stability of a frisbee
those are almost everything to the fact
that it's actually spinning and that
spinning keeps it it keeps it oriented
in a particular plane what we should do
is work out where velocities are coming
at the end of it so one way to do that
and I advise anybody who gets one of
these for Christmas any of you is a
budding science
go out and do this get a high-speed
camera it might be a bit expensive
you could bug your parents for that as
well get a ruler get lots of light and
then just stick a ruler at the the the
exit of the gun
what's it called what's it called the
exact barrel no they ended the barrel
the muzzle the muzzle of the gun and
then work out just how fast they they
come out of that you've got its angular
momentum is directed like this and it
doesn't really want it takes an awful
lot to actually perturb it from that it
really wants to and it actually if you
if you turn it away from that it will
restore itself back to the the plane it
was in it's just like if you're riding
on a bike it's very very difficult if
you're just trying to stay a static on a
bike you'll go to one side but if you
actually riding up bike you could
angular momentum on the wheels then you
know you stay you've got a much greater
deal of stability it's exactly the same
here so if this is static it's pretty
unstable and it will flip over if it's
spinning it's much more stable I looked
up the position like they do in the wall
actually I'll try and catch them it's it
is very physics loaded so in terms of
you've got a spring-loaded clip
obviously you've got the elastic energy
stored in this spring loose spring
loaded clip and what that is doing is
releasing the disc into the barrel of
the gun and then it's being driven
forward as a motor here oh let's not
break it so you can hear that generating
I don't if you're going to see much
unfortunately and it's that which
generates the force which spits this
thing thing out I think what Christmas
presents of a huge amount of physics and
let me see what did I get
I was pretty nerdy as a young boy so the
Christmas present I got was a microscope
and I got a chemistry set and I got a
physics set but toys any toy any simple
toy or even a scooter or a bicycle
physics that's that's what controls the
motion
yep practically everything in the world
everything in the universe you can break
down to physics
so whose Christmas present is that
that's nobody's Christmas present so my
son is three years old he's too young
for this but I don't think I buy it for
him anyway in the first place I think
it's for older kids what are you going
to do with it there so that is going to
remain in the department and we can use
it for various different demonstrations
in fact might well bring it into
lectures and keep the undergraduates
under control it'll be quite good
because at the moment if they fall
asleep or they make noise I poke them
with a big stick this would be much more
fun