Lesson 8 of 12 · Forces
Hooke's Law and Elastic Limit
🏋️
🎯 Your mission
Set it up. Test it. Be amazed.
⚡ The twist
Energy never disappears — it just hides somewhere else.
What you'll learn
For a spring below its elastic limit, extension is proportional to load: F = kx, where k is the spring constant in newtons per metre. Beyond the elastic limit the line bends and the spring no longer returns to its original length.
Key words
spring constant
The stiffness of a spring, k, in newtons per metre.
elastic limit
The load beyond which a material no longer returns to its original shape.
Make a hypothesis first
Before you start: which will move faster, and why?
Say your guess out loud — then find out if you were right.
Get ready
🧰 What you need
- spring
- slotted masses
- clamp stand
- metre rule
- graph paper
Get ready
⚠️ Safety first
- Wear eye protection: an overloaded spring can snap back.
- Weight the base of the clamp stand and keep feet from under the masses.
Step 1 of 4 · Read
Think about what you just learned: say what "spring constant" and "elastic limit" mean in your own words before you start.
Step 2 of 4 · Do
Hang increasing masses on a spring and record extension each time. Plot force against extension, take the gradient as k, and keep loading in small steps until the graph departs from a straight line — that point is the elastic limit.
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
Question 2 of 2
Mind = blown
🎢 You feel weightless on a roller coaster because you and the seat are falling at the same speed.
Nice work!
You got 0 of 2 right.
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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.”
Share this experiment
Send it to a parent who's looking for a 10-minute kitchen science win.
Ready?
Hooke's Law and Elastic Limit
Set it up. Test it. Be amazed.
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Print the whole Forces track
All 9th Grade Forces lessons as a printable PDF, with worksheets and answer keys.