🎱 Does a higher start make a marble roll faster?

My hypothesis

If I change how high up the run the marble starts, then how fast the marble crosses 2 m of floor will ______, because ______.

🔊 You fill in the blanks. Think about where the marble's speed comes from, and how far it has dropped by the time it reaches the floor. 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

• 🧻 Cardboard tubes: 3
• 🔮 A marble
• 🩹 Masking tape, to mark lines
• 📏 A tape measure, or a long ruler
• ⏱️ A stopwatch or a kitchen timer
• ✂️ Kid scissors
• 🩹 Tape

Steps

1. Cut three cardboard tubes in half the long way to make six slides.🔊
2. Tape the slides down a wall in a zigzag, the last one ending right at a hard floor.🔊
3. Mark the three start spots with masking tape: the slides 40, 80 and 120 cm up.🔊
4. Put a tape line on the floor where the run ends, and another 2 m farther on.🔊
5. Lay a folded towel past the second line to stop the marble.🔊
6. Set the marble in the run at 40 cm and let go without a push.🔊
7. A helper starts the timer as it crosses the first line and stops it at the second.🔊
8. Write the time down, then do it two more times.🔊
9. Do three runs from 80 cm and three from 120 cm.🔊
10. Work out each speed: 200 divided by the seconds gives cm per second.🔊
11. Find the mean speed for each height 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 marble that has been lifted up stores energy, and as it rolls down that energy turns into speed. Starting higher gives it more energy to turn into speed, so it usually crosses the floor faster. Twice the height gives twice the energy but less than twice the speed, and each slide rubs some away, so your line may bend and flatten.

Going further (7th and up): Change a second thing: tilt every slide more steeply, run all three heights again, and draw both lines on one graph.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 3rd grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed how high up the run the marble starts and measured how fast the marble crosses 2 m of floor, in cm per second.
• What did you keep the same, and why does that matter? I kept the same marble and letting go without a push the same, so the only difference was how high up the run the marble starts.
• 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 tilt every slide more steeply, run all three heights again, and draw both lines on one graph.

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

• 🚗 Does a steeper ramp make a toy car go farther?2nd–6th grade · 1 day of testing · free🚗 How things move · ✂️ Paper, tape and toys
• 🎯 Does a longer arm make a catapult throw farther?3rd–8th grade · 1 day of testing · free🚗 How things move · ✂️ Paper, tape and toys

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