🥤 Does a wider base keep a cup tower from tipping?

My hypothesis

If I change how wide the bottom of the tower is, then how many books go under the board before the tower tips will ______, because ______.

🔊 You fill in the blanks. Think about where the middle of the tower is, and when it hangs out past the bottom cups. A guess is a good because: the test finds out.

Change, measure, keep the same

Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 3 levels 3 times.

What you need

• 🥤 Paper cups: 12, all the same
• 📦 Flat cardboard: a big flat piece, about 60 cm long
• ✏️ A pencil
• 📚 Some books: about 15, all about the same thickness
• 🩹 Tape

Steps

1. Stack four paper cups into a column, rim to rim then bottom to bottom, and tape each join.🔊
2. Make two more columns the same way.🔊
3. Tape a pencil across the cardboard near one end, and lay the board on the floor.🔊
4. Stand one column on the board, right against the pencil.🔊
5. Slide books under the far end of the board, one at a time, very gently.🔊
6. Count the books when the column tips over, and write the number down.🔊
7. Do it two more times.🔊
8. Tape two columns together and stand them against the pencil, one behind the other.🔊
9. Do three tests, then tape on the third column the same way and do three more.🔊
10. Find the middle number for each width and draw a line graph.🔊

Every step is one you can do yourself, with a grown-up nearby. Write each number down straight away, in the table below, so nothing is lost.

Your results table

From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a line graph, because the thing you change is a number that goes up.

Why it works

🔊 A tower tips when its balance point, the middle of its weight, moves out past the edge of its bottom cups. Tilting the board slides that balance point toward the downhill edge. A wider base puts that edge farther away, so the board has to tilt more before the tower goes over.

Going further (7th and up): Change a second thing: build each width three, four and five cups tall, and draw a line for each height.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 2nd grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed how wide the bottom of the tower is and measured how many books go under the board before the tower tips, in books.
• What did you keep the same, and why does that matter? I kept the same height: four cups tall and the same cups, taped the same way the same, so the only difference was how wide the bottom of the tower is.
• How many times did you test it? 3 times at each of my 3 levels.
• If you did it again, what would you change or test next? I'd build each width three, four and five cups tall, and draw a line for each height.

Make it yours

Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.

Try next

• 🌉 Which paper bridge shape holds the most coins?2nd–7th grade · 1 day of testing · free🚗 How things move · ✂️ Paper, tape and toys
• 🥚 Which padding keeps a dropped egg from cracking?3rd–8th grade · 1 day of testing · about $3🚗 How things move · 🧂 Kitchen things

🔨 From the Workshop: this project grows from a Workshop build, with picture steps of its own.