⚖️ Balancing a ruler lever: the whole packet

⚖️ Balancing a ruler lever · 4th–8th grade · 1 day of testing · free · 45 minutes a sitting

My days, if the fair is 14 days away

Count back from your fair day and write in each date. Fewer days than this? The jobs share days, in this order; nothing is skipped.

Dates from my teacher

• My question is due
• Testing starts
• My results table and graph are due
• My board is due

In this packet

1. 🗓️ My project plan
2. 💭 My hypothesis
3. 🧺 Change, measure, keep the same
4. 🪜 My steps
5. 📊 My results
6. 📓 My logbook
7. ✅ My conclusion
8. ✂️ Board titles to cut out
9. 🏅 The judge's questions and my certificate

If I change how many pennies are in the stack on the right, then how far from the pencil the stack must sit to balance the ruler will ________________, because _____________________________________________

What I think will happen, in my own words:

4 levels × 3 tries at each = 12 tries in all. If anything you keep the same changes, you won't know which change made the difference.

What I need

• 🪙 Pennies: about 25
• ✏️ A pencil
• 🩹 Masking tape, to mark lines
• 🩹 Tape
• 📏 A ruler

Be safe: 👶 Small parts

1. Tape a pencil to a table so it cannot roll.
2. Slide the ruler across the pencil until it sits level, and write down the number over the pencil.
3. Tape pennies into stacks of 2, 4, 6 and 8, and one more stack of 4.
4. Tape the extra 4-penny stack to the ruler, 6 cm to the left of the pencil.
5. Set the 2-penny stack on the right side and slide it until the ruler sits level.
6. Read the number under the stack's middle and take away the pencil's number: that's the distance.
7. Write it in your table under Try 1, then lift the stack off and find the balance two more times.
8. Do three tries with the 4-penny stack, then the 6-penny stack, then the 8-penny stack.
9. Find the mean for each stack and draw a line graph.

Write each number in your results table the moment you measure it.

I changed: Pennies on the right   I measured: how far from the pencil the stack must sit to balance the ruler (cm)

MY GRAPH (a line graph: pennies on the right along the bottom, cm up the side)

What I noticed: ______________________________________________

Write something every day you work on it, even the days you only gather things. More days? The three-page logbook prints from peabody.kids/science-fair/templates/logbook.

My hypothesis was ☐ right ☐ partly right ☐ not right.

I know because my numbers show:

What surprised me, or what might have gone wrong (7th and up):

Next time I would test:

Idea: Change a second thing: move the left stack to 4 cm and to 8 cm, repeat all four tests for each, and draw the lines on one graph.

1. What made you want to ask this question? Say something like: I wanted to know: where must pennies sit to balance a ruler?
2. What did you think would happen, and why? Say something like: I thought changing how many pennies are in the stack on the right would change how far from the pencil the stack must sit to balance the ruler, and I wrote down why.
3. What did you change, and what did you measure? Say something like: I changed how many pennies are in the stack on the right (2 pennies, 4 pennies, 6 pennies, 8 pennies) and measured how far from the pencil the stack must sit to balance the ruler in cm.
4. What did you keep the same, and why does that matter? Say something like: I kept the same ruler on the same pencil and four pennies taped 6 cm to the left of the pencil the same, so only how many pennies are in the stack on the right was different.
5. How many times did you test it? Say something like: 3 times at each of my 4 levels, and I found the middle number.
6. What did you find out? Show me in your numbers. Say something like: Look at my table: 2 pennies and 8 pennies gave different numbers, and here's the pattern.
7. Was your hypothesis right? How do you know? Say something like: My numbers show whether I was right, partly right or not, and I can show you where.
8. Did anything go wrong, or surprise you? Say something like: One try was odd, so I did it again and wrote it in my logbook.
9. If you did it again, what would you change or test next? Say something like: I'd change a second thing: move the left stack to 4 cm and to 8 cm, repeat all four tests for each, and draw the lines on one graph.