Moments and Turning Forces

Lab Brief #7

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

The opposite of what you expect is often what happens.

What you'll learn

The moment of a force about a pivot is force times perpendicular distance, in newton metres. A balanced object obeys the principle of moments: total clockwise moment equals total anticlockwise moment. That is why a long spanner loosens a tight nut.

Key words

moment
The turning effect of a force: force times perpendicular distance from the pivot.
pivot
The fixed point about which an object turns.

Make a hypothesis first

Predict: what happens if you double the force?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

metre rule
pivot or knife edge
slotted masses
hangers

⚠️ Safety first

Keep masses low over the bench so a slip cannot drop them on toes.

Step 1 of 4 · Read

Think about what you just learned: say what "moment" and "pivot" mean in your own words before you start.

Step 2 of 4 · Do

Balance a metre rule on a pivot at its centre, hang masses at measured distances on both sides, and adjust until it balances. Record five balanced arrangements and check that force times distance matches on each side.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

The moment of a force is calculated as:

How sure are you?😐 maybe

Question 2 of 2

Why does a longer spanner make a nut easier to turn?

How sure are you?😐 maybe

Mind = blown

🔥 A bolt of lightning is 5 times hotter than the surface of the sun.

Nice work!

You got 0 of 2 right.

Next: Hooke's Law and Elastic Limit All lessons

🎯

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✨ More to explore

🌍 Where you see this in real life: This is why airplanes can fly and why rockets reach space.

🏆 Stretch challenge (try it this week): This week, find one thing in your house that turns one kind of energy into another.

👨‍👩‍👧 For the dinner table: “Show me something at home that uses this kind of energy.”

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