Hello, I am Jared. Welcome to Fun Science Demos. Today we have a STEM design
challenge here at FunScienceDemos. We try to build simple things with simple
materials and today we are going to a try and build a catapult with nothing but binder
clips and rubber bands. some catapult designs can be really
complicated and you need hot glue and you need all kinds of different
materials to make it work, and some catapault designs are really simple
but they do not work that well. well, we think we can create a catapult with just
these materials that works really well! now, to build a catapult, we need an
energy source, and you may think that the energy source for our catapult is going
to be the spring in this binder clip, but it is not. this binder clip is actually
just going to hold our energy source: a rubber band or two. now, I can put energy
into a rubber band simply by stretching it. there is a lot of energy in there, and
I can shoot it and watch it fly across the room. I need to stretch this rubber
band around this binder clip so that I can harness the energy in that rubber
band. here is how we do it. so we have zoomed in so you can see how this works. so
we are going to hold our binder clip up, and we have these two arms. notice the the
gap between the two arms. all I am going to do is pinch the rubber band and slide it
through those arms. now comes the stretching part. so I am going to hold one
end of my rubber band and I am going to stretch the other one over top of those
arms. okay, now I am going to stretch the bottom over top, and now I have a
stretched rubber band. I need to stretch it even more to get this to work. believe
it or not our catapult is almost ready to go. you can see how it works here. I have
a rubber band that is stretched around the arms, but I need to stretch it even
further by pulling this arm back, and you can see my rubber band stretch. now it is
hard to hold and I am going to need to have some kind of base that I can pinch
in between the binder clip, but here you can see our catapult in action. if I let
go of this it launches. so we have our catapult, but we need a base to stabilize
that catapult. so I am thinking we could use a ruler, a deck of cards, a roll of
tape, anything that would work. now, the about this binder clip: you will notice the
ruler is just a little too small, or if I made my catapult out of a smaller binder
clip that would be perfect. so, I am going to try, using the roll of tape, I am going to
squeeze this, and now I have a nice secure solid base where I can pull back
my catapult. and you can see it stays by itself because I can actually wedge it
in under the tape, and I just flick it and it launches. now we need something to
launch. we could use mini marshmallows, we could use cheese balls, we could try a
ping pong ball, we could try little tiny goldfish (crackers), but we
decided we are going to go with a little rubber eraser because it is soft, and it is
safer. we have zoomed in so you can see why our rubber erasers are perfect: they are
the perfect size to rest right on that arm of that binder clip. I do not even
need to build a platform to hold whatever I am going to launch. it is all
ready to go, and you can see it launches. so our catapult is loaded and ready to
launch. let us see what happens: three ,two, one! it happened so quickly because my my
catapult is pretty powerful, but it actually flipped forward and held on to
this eraser and launched it straight into the table and ended up bouncing.
that means it is releasing this too late. I need it to release that sooner, so that
I can get a nice high arc. so we have to fix some things.
so we have taken our rubber band, our energy source, off our catapult so we can
talk about what is going on. what is happening is I load the rubber eraser,
it is staying on the platform too long, and when it gets to here it is throwing
our eraser down onto the table. so I have to change the angle at which this thing
launches. so I could angle up my whole launch pad and see if that actually
makes a difference, or I could put something in my catapult which prevents
the arm from coming all the way forward, and forces it to launch it higher. I
could try something like a pencil, but we are going to try something a little bit
bigger. we are going to try getting this piece in there so that we get a
different release angle. let us see what happens. so here is what we came up with:
to modify our catapault to see if we can get it to launch at a different
angle. we wedged in this little thing, and we are
going to try and see what happens. stretch it back, place on my eraser, I am
going to angle it a little bit, three, two, one, yes! there are so many things we can do with
this design. if this it is not strong enough I could stretch another rubber band. I will
double it up, stretch it over. I could try three rubber bands, I could
try four rubber bands, I could actually measure the distance to see how much
further my projectile goes once I add a rubber
band. now, the one thing you will probably find as you continue to launch is that
this rubber band really gets stretched. and they do break, so you are going to need
a good supply of rubber bands because you will go through the rubber bands. now,
this is a big binder clip. these smaller binder clips are easier to find let us
see how these work. so, now I have my smaller catapult, smaller binder clip,
same stretched rubber band, I put two rubber bands on this time and you will
notice I slid a pencil to change the launch angle. now all I need is a base,
and I can get my ruler, and now I am ready to go. let us see how this one works. we are
going to launch it sideways: three, two, one, let us try another one. straight at the
camera: three, two, one. these things are really moving quickly. so, so far we have
been able to make our catapult better by going back and redesigning, but we have
also noticed that it was hard to balance our little rubber eraser on that small
arm of our binder clip, so what if we made some modifications to that? what if
I put a little tiny piece of tape to make kind of like a little cradle to
hold that clip? let us see if that actually works. a little better, yes. it
balances beautifully on that. let us try shooting it: three, two, one, perfect. we
could also try using a paper cup. now here is what I am going to do: I am going to cut
down the side, but leave the bottom on the cup, with a little bit on the back
part of the cup. so I am going to cut down,
I am going to cut down now making sure to leave on the bottom, I am just going to
cut that outer side of the cup off, and now I have a little basket, that if I can
attach it, should be able to hold my eraser. let us try attaching this. so, then
all I had to do with a paper cup was tape it to my arm because I am pretty
sure it will fly off if I do not tape it to the arm. and now I have a nice little
basket that should hold this, and see what kind
of launch we get: three, two, one, perfect. the other nice thing about using this
paper cup to make a little holder for my catapult, is I can use this to launch
more than one thing. let us see what this does:
three, two, one, with a few rubber bands and a binder clip you can build your own
catapult. now, I have to warn you: with a lot of rubber bands, this rubber eraser or
whatever you decide to launch, will go far. it could go 5, 10, 15 meters. I have
actually launched this all the way across my classroom, and bounced it off
the wall. they are so much fun. if you want to learn some more stem design
ideas, check out our YouTube channel, FunScienceDemos.
Science is so cool, thanks for watching.