One.

Hi, I'm Nick from Design Squad Global.

We're at the Acera School, and we're building catapults.

(drilling) Catapults are really cool.

For example, you could throw a tuna fish sandwich to your friend who doesn't have one who could be very far away.

You could also use a catapult to fling snowballs when you're having a snowball fight.

You would totally win.

We're making our catapults out of wood, paracord, bungee, and really anything else we can find around the wood shop.

Most catapults use levers.

When the lever is pulled back, it gets loaded with potential energy.

When the lever is released, the potential energy is converted to kinetic energy, which is the energy of motion.

Most of this kinetic energy goes then into the object-- in our case, a ball-- which then gets hurled through the air.

We're going to see whose team can fling a tennis ball the farthest.

And I don't want to give anything away, but it's going to be my team.

So the kind of catapult that we're working on is this big slingshot that's kind of like a triangular shape.

Instead of using rubber bands, we are using bungees.

And when you pull back and let go, it'll shoot forwards, and we're going to use a tennis ball and see how far that can go.

So the reason why we're lashing the wood together, which is kind of like tying the wood, is because it will not ruin the wood so we can reuse it in later projects, and it won't cut the wood or put holes in the wood, and it's easy to put together and take apart.

- The kind of catapult we're working on is called a trebuchet.

It uses gravity to launch the tennis ball.

We're redesigning a trebuchet that I had made last year with some middle schoolers.

Now we're basically upgrading it.

This weight here goes into that pole up there.

When we release it, the short part of the lever goes down, the long end of the lever goes up, pulling this pouch and ball along the track.

And as the arm gets to a certain point, the ball will be thrown out that way.

(drilling) Yeah!

So the initial design had a pail hanging with rocks for the counterweight.

This year, we've redesigned it to have this bar that holds barbell weights.

Our old boom pole was five feet, 11 inches.

Our new boom pole is over ten feet.

- Wait, I have an idea.

This is a really good idea.

I'm feeling it.

- So right now we're trying to figure out how to attach the can to the bungee cord.

- Let go.

(laughing) Okay, hold on, here.

The problem right now is that the can keeps turning around, and we can't keep it straight, so the ball keeps flying backwards, and that's a problem.

- So because the can was bouncing around a bunch before, we decided to add some metal pipes to string the bungee through to stabilize it.

All right, let's try it.

That was not good.

- No.

We got to figure something else out because this is not working.

Okay, here's our first test, just to make sure it works.

- Three, two, one!

- It works!

- It actually works.

- Yes!

- It worked better than I thought it was going to.

The tennis ball went pretty far.

Now we're going to add some more weight, and maybe it will make it fling farther.

More weight, more potential energy, more kinetic energy.

We tried using the tin can to hold the tennis ball, but it really didn't work.

So now we're using a leather pocket to hold the tennis ball instead.

- Hopefully this leather pouch will work better than the can.

- First test.

- Wow.

- Much better.

Okay, we're all set up.

It's slingshot versus trebuchet and slingshot's going to win.

The trebuchet is going to destroy that slingshot.

Go Team Slingshot!

Go Team Trebuchet!

Okay, here we go, we're going first.

Three, two, one, lift it up.

Whoo.

Three, two, one.

So I guess you could say team trebuchet won because theirs landed farther.

If I could make this again to make it better, I would have it so that my slingshot can go further to the ground so that it gets more air.

If we could build this again or improve it, I think we would add more weight so that there would be more counterweight, so it could go way farther.

(cheering, laughing)