Who’s up for a challenge?

Squeaks and I love to build things. Sometimes we build forts out of pillows … or castles out of blocks...and sometimes we snap together plastic bricks to make spaceships!

But, today we’re going to use cups. Yup, just cups! And Squeaks and I have decided to build the tallest stack of cups that we can.

We know from playing with blocks, that it’s best to build our stack on a flat, hard surface...like a piece of floor that doesn’t have any carpet on it. And to make things easier, we’re going to use cups that are all the same size. And, we’re going to use plastic cups.

Paper cups would work, too...just never glass. Looks like we’re ready, Squeaks. Let the cup stacking begin!

First, we’ll start by putting a cup upside down on our table. You can use the floor, or a table at home.  Next, we’ll put another cup on top. We’ll need to put this one right-side up, so it doesn’t slide down on top of the first one.

Now, we’ll carefully set another cup, cup number three, upside down on top of number two. Cup four goes on top, right side up. Hmm, things are getting little wobbly.

Cup number five goes on...successfully! Let’s see if we can put cup number six on top...and down it goes! So, by making a simple stack of cups, one on top of the other, we were able to build a tower that was five cups high.... before it fell over.

But, what can we do to build a tower that’s even taller? We’ll need to find a way to make our stack of cups more stable. If our stack of cups is stable, that means it won’t wobble and sway like our last stack did, so it shouldn’t fall over as easily!

So this time, let’s try something different. Let’s start with three cups, upside down on the table. Now we’ll put two cups -- also upside down -- on top of those … and we’ll put one more cup on the top.

Look, we made a pyramid! This stack is one...two...three cups tall. Do you see how our pyramid of cups is shaped like a triangle?

It has a big, wide base, or bottom. That wide base is a reason that a pyramid...and our second stack of cups... is so stable. You can test this out for yourself.

But not just with cups. With you! Stand up for a minute!

Now, try to stand on one foot. Do you wobble back and forth a little? Now try standing on both feet.

It’s probably easier to stand on two feet, right? That’s because two feet make a wider base than one foot. Your weight is spread out between both feet instead of being all on one foot.

The same thing is true when you’re building something -- whether it’s a stack of plastic cups, or a big-city skyscraper! In our first tower, the weight of the stack was on the one cup on the bottom. But in our second try, the weight of the stack pushed down on three cups that were spread apart, instead of one.

A wide base helps to spread out the weight of what’s on top of it, and makes whatever you’re building more stable. So let’s try one more building, using an even wider base. We’ll put one, two, three, four, five cups on the table.

Then, we’ll pile four more on those...then three...then two...and one on top. This time our pyramid is five cups high! In fact...if we start with even more cups on the bottom of our pyramid, you can build even higher!

That wider base makes it possible to build a taller structure. A wide base is useful for more than just stacking cups. Some of the most stable buildings in the world are shaped like pyramids.

This building is one of the tallest in San Francisco...and is stable enough to stay up during an earthquake. So, are you excited to build your own stack of cups? Ask a grownup to help you find some cups...and you’re set to get stacking!

Thanks for joining me on SciShow Kids! Do you have a question for us about buildings...or anything else? If you do, ask someone to help you to leave a comment on this video, or to send an email to kids@scischow.com!