Science Fair

Grown-ups

Does a longer string swing slower?

4th–8th grade · 1 day of testing · free · ages 9 to 14 · 45 minutes a sitting

  • 👶 Small parts
What you need for the pendulum length and swings project: string or yarn, pennies, a pencil, a stopwatch or a kitchen timer

My hypothesis

If I change the length of the string, then how many swings it makes in 15 seconds will ______, because ______.

You fill in the blanks. Think about how far the weight has to travel on each swing when the string is longer. A guess is a good because: the test finds out.

Change, measure, keep the same

CHANGE

the length of the string: 20 cm, 40 cm, 60 cm

MEASURE

how many swings it makes in 15 seconds, in swings

KEEP THE SAME

  • the same weight on the end
  • letting go from the same distance out to the side
  • counting for the same 15 seconds

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

  • String or yarn: about 80 cm
  • Pennies: 5
  • A pencil
  • A stopwatch or a kitchen timer
  • 🩹 Tape
  • 📏 A ruler

Steps

  1. Tape five pennies together into a little stack: that's the weight.
  2. Tape a pencil to the edge of a table so it sticks out.
  3. Tie the string to the pennies and hang them from the pencil, 20 cm long.
  4. Pull the pennies out to the side until the string is straight, then let go.
  5. A helper times 15 seconds while you count the swings: over and back is one.
  6. Write the count down, then do it two more times.
  7. Make the string 40 cm and count three times, then 60 cm.
  8. Find the mean for each length 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

MY RESULTSPeabody 🦉 peabody.kids/science-fair

Name ______________________ Fair day ____________

Question: Does a longer string swing slower?

I changed: String length   I measured: how many swings it makes in 15 seconds (swings)

String lengthTry 1 (swings)Try 2 (swings)Try 3 (swings)Mean
20 cm
40 cm
60 cm

MY GRAPH (a line graph: string length along the bottom, swings up the side)

What I noticed: ______________________________________________

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.

📊 Make my graph🖨 Print the whole packet (9 pages)

Why it works

A pendulum swings because gravity keeps pulling the weight back toward the middle. A longer string makes a bigger arc, so each swing takes longer and you count fewer in 15 seconds. Galileo noticed this about four hundred years ago, and pendulum clocks are set by the length of their pendulum.

Going further (7th and up): Change a second thing: keep 40 cm and hang 3, 5 and 8 pennies. Does the weight change the count?

Board layout

MY BOARD · 36 × 48 in tri-foldPeabody 🦉 peabody.kids/science-fair
  1. ❓ Question (10 × 8 in): Does a longer string swing slower?
  2. 💭 Hypothesis (10 × 9 in): If I change the length of the string, then how many swings it makes in 15 seconds will ______, because ______.
  3. 🧺 Materials (10 × 12 in): 4 things: see your list.
  4. 🪜 Steps (22 × 9 in): 8 steps, three tries at each level.
  5. 📊 Results (22 × 16 in): Your table (String length down the side, tries across) and your line graph.
  6. ✅ Conclusion (10 × 14 in): My hypothesis was right / partly right / not right. I know because…

Materials to list: String or yarn; Pennies; A pencil; A stopwatch or a kitchen timer.

Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.

This project at your grade

4th–6th gradeTries: three at each level. The table: units in the header and a mean column. The graph: a bar graph, or a line for a number that grows. The conclusion: right, partly or not, and the numbers that show it.
7th grade and upTries: three or more at each level. The table: a mean for every level of both tests. The graph: a graph with two lines or two sets of bars. The conclusion: the numbers, what might have gone wrong, and a next question. Second variable: keep 40 cm and hang 3, 5 and 8 pennies. Does the weight change the count?

Every grade this project fits works out a mean. See every project for 4th grade, or print a blank results table.

What a judge will ask

  • What did you change, and what did you measure? I changed the length of the string and measured how many swings it makes in 15 seconds, in swings.
  • What did you keep the same, and why does that matter? I kept the same weight on the end and letting go from the same distance out to the side the same, so the only difference was the length of the string.
  • 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 keep 40 cm and hang 3, 5 and 8 pennies. Does the weight change the count?

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

👨‍👩‍👧 For grown-ups and teachers: how much to help, the safety rules, and running a school fair. Science fair v0.16.1 · Checked .

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