Kind: captions
Language: en
[Applause]
I am here at the University of Sydney
where the mechanical engineering shop
has built this incredible piece of
apparatus for me it is a 40 lb that is
19 kg flywheel on the end of a meter
long shaft can you imagine trying to
hold this out horizontally with just one
hand at this end it is virtually it is
impossible okay now I'm going to let go
you going to be able to hold this at all
I right
side can you lift it out make it
horizontal hold it hold it hold it come
on just try to I want you to hold it out
horizontal see if you can hold it hold
it ah come
on what I'm going to do is I'm going to
spin this up to a few thousand RPM and
then I'm going to attempt just that to
hold it from one end and have it out
horizontally 5 4 3 2 one boom
I'm going to lick go with my left hand
what you'll see is that the shaft
remains horizontal and see it going
around there it almost looks as though
the wheel is weightless how does this
work well instead of pulling the wheel
down to the ground as you'd expect the
weight of the wheel creates a torque
which pushes it around in a circle you
may recognize this as gyroscopic
procession for a more detailed
explanation Click The annotation or the
link in the description to see my video
on the topic here I want want to try
something more extreme I'm going to try
to lift it over my head with one hand
while it's spinning wish me luck but
before I make the attempt Rod wisely
suggests that I first check if I can
lift the wheel above my head without it
spinning let's prove that I can lift it
just this end without it spinning here
we
go how I mean it's just kind of awkward
with the
hand
careful justful
just barely oh goodness do you even lift
ah clearly I do not undaunted by my lack
of strength I'm going for it but I want
to make sure that the wheel is spinning
as fast as possible to give me the best
chance of success keep give it 10 more
seconds 10 9 8 7 6 5 4 three two one go
that was perfect now I'm going to
release my left hand and holding only
with my right hand at the end of the
shaft I'll try to lift it up over my
head this is a 40 lb 19 kg flywheel
ready here we go 3 2
[Music]
1 beautiful let's go again in three 2
1 nice
3 2
1 it feels incredibly incredibly light
as I do that
[Applause]
[Music]
when you said it felt incredibly light
and when you're lifting it feels light
yeah shouldn't I
know honestly I have lifted it up with
one hand when it's not spinning and it
feels really hard to lift it up like
it's a big effort yeah but with this
when it's spinning it honestly felt like
it was just wanting to go up by itself
yes it felt like I was not struggling
like I was not putting in the amount of
force that You' think to lift that kind
of weight
I bet if you let it go it crash down to
the ground that's not white on we can't
do that though we can't do that part of
the experiment what we could maybe do is
I could stand on a scale and we could
see what the weight of me plus that
apparatus does while I'm lifting it up
over my head see if I get lighter in
essence you can see that just my weight
is about 72 kg now when I pick up the
flywheel it goes up to
about 91 kg which makes sense cuz the
flywheel itself is about 19 kilos that's
42 LB now we're going to spin it up and
I want you to make a prediction as I'm
lifting it over my head do you think the
scale reading will be more less than or
equal to 91
kg what do you think you can make your
prediction by clicking on one of the
onscreen annotations or if you're on
mobile you can click a link in the
description five 4 3 2 1
sh