What If? Lab
What if there were no springs?
Springs squash and bounce back. They are hiding in beds, pens, clocks and cars. What if there were none? Let's imagine it with Olly!
A spring stores energy when you squash or stretch it, then gives it back as it springs into shape. Imagine a world with no metal springs at all, and follow what would happen to bouncy beds, clicky pens, old-style clocks and car rides.
A spring obeys Hooke's law, F = −kx, and stores elastic potential energy ½kx². This thought experiment removes coiled metal springs from everyday machines and asks which jobs other parts could take over and which would get much harder.
The big question
Push a spring down. Let go. Boing! It jumps back.
Springs are hiding in lots of things. What if there were no springs at all?
Squash a spring and it pushes back. Stretch it and it pulls back. Let go, and it snaps back to its shape. That simple trick is hiding inside beds, click pens, mechanical watches and cars.
So what if metal springs had never been invented? This lab is a thought experiment: we follow the ideas one step at a time, and each card says whether it is a measured fact or a careful idea.
A spring is a device built to deform elastically: displaced by x from its resting length, it supplies a restoring force proportional to x and stores the work done on it as elastic potential energy.
This thought experiment removes coiled metal springs from everyday technology. The physics of springs comes from measured, textbook relations; what people would build instead is reasoning, labeled as ideas.
Explore the idea
Make a prediction
You squash a spring and let go. What does it do?
You squash a spring and then let go. What happens?
A compressed spring is released. What happens to its stored elastic energy?
- It springs back and pushes
- It stays squashed forever
- It melts
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Established fact
Springs push back harder the more you squash them.
Hooke's law: the farther you squash or stretch a spring, the harder it pushes or pulls back.
F = −kx; stored energy ½kx² (OpenStax).
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An idea scientists discuss
A world without springs is pretend. We imagine it carefully.
Springs won't really vanish. What people would use instead is an idea built from how springs work.
Every replacement in this lab is reasoned from what springs do, not observed.
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Established fact
The more you squash a spring, the harder it pushes back.
A spring pushes or pulls back harder the farther you squash or stretch it. This is called Hooke's law.
Hooke's law: F = −kx, a restoring force proportional and opposite to the displacement (OpenStax).
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Established fact
A squashed spring holds energy.
Squashing or stretching a spring takes work, and the spring stores that work as energy until it springs back.
Work done deforming a Hooke's-law system is stored as elastic potential energy, PE = ½kx² (OpenStax).
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Established fact
Springs turn a squash into a push.
When a squashed or stretched spring is let go, it turns its stored energy into movement.
On release, a spring converts elastic potential energy into kinetic energy (OpenStax §16.1).
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An idea scientists discuss
Beds could be soft with foam instead.
Beds could still be soft using foam, wool or feathers, but trampolines might not bounce as high without springs.
Cushioning only needs a compliant material; strong rebound needs efficient energy storage, which other materials might or might not match.
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Established fact
Springs helped clocks become small enough to carry.
Between 1500 and 1510, spring-powered clocks replaced heavy weights, so clocks and watches could become small and portable.
NIST credits Peter Henlein of Nuremberg with spring-powered clocks (1500–1510); dropping drive weights allowed portable watches, though they slowed as the mainspring unwound.
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Established fact
Modern clocks can keep time without springs.
Modern clocks keep time with a balance wheel, a pendulum, a vibrating crystal or even atoms.
NIST lists the balance wheel, pendulum, vibrating crystal and atomic transitions as the regulators of modern clocks.
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Established fact
A click pen has springs inside.
A classic click pen uses two springs to push its parts into place each time you click.
In the first Parker retractable pen (1954), two springs force the cam into position as the pen is clicked out and back (Make magazine).
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An idea scientists discuss
Pens might just have caps.
Without springs, pens might use caps or twist mechanisms, and clocks might use weights, pendulums or batteries.
Twist and cap designs avoid springs; whether a clean click mechanism could be made from flexing plastic alone is an open engineering question.
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Established fact
Cars sink a little on their springs when someone gets in.
In a physics textbook example, a car sinks about 1.2 centimeters on its springs when an 80-kilogram person climbs in.
OpenStax's example: a car settling 1.20 cm under an 80.0 kg person has k ≈ 6.53 × 10⁴ N/m.
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Established fact
Shock absorbers stop a car from bouncing and bouncing.
Without shock absorbers, a car would keep bouncing on its springs. A bouncy car is a sign of worn shock absorbers.
Damping from shock absorbers stops the oscillation; 'bouncing cars are a sure sign of bad shock absorbers' (OpenStax).
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An idea scientists discuss
Rides might be very bumpy.
Without springs, car rides might be bumpy and shaky, and roads might need to be extra smooth.
Engineers might turn to rubber or air-filled cushions; how well these could replace steel springs is speculation here.
In our world
When you squash a spring, it pushes back.
The harder you squash, the harder it pushes. Then it bounces back to its shape.
Springs follow a neat rule called Hooke's law: the farther you squash or stretch a spring, the harder it pushes or pulls back. Pull it twice as far and it pulls back twice as hard.
A spring also stores the energy you put into it. Squashing it takes work, and that work is saved inside the squashed spring until it springs back. Car springs are a good example. A physics textbook works out that a car can sink about 1.2 centimeters on its springs when an 80-kilogram person climbs in.
Hooke's law, F = −kx, says the restoring force is proportional to the displacement and opposite to it; the force constant k, in newtons per meter, measures stiffness. If deformation is the only result, the work done is stored as elastic potential energy, PE = ½kx².
OpenStax's worked example: a car that settles 1.20 cm when an 80.0 kg person gets in has a suspension force constant of 784 N ÷ 0.0120 m ≈ 6.53 × 10⁴ N/m. Without damping, the car would keep bouncing up and down.
Take the springs away
In our pretend world, Olly takes every spring away.
What would happen to beds and pens? What about clocks and cars?
In our pretend world, every coiled metal spring is gone. Rubber, wood and plastic can still bend a little and spring back, but there are no springs made just for that job.
Follow the paths: beds and trampolines, clocks and pens, and cars on bumpy roads. You will see that some jobs could be done another way, while others would become much harder.
Here coiled metal springs vanish, but elasticity itself remains: every solid deforms elastically to some degree, as a plucked plastic ruler shows when it vibrates back and forth.
The question is therefore engineering, not physics: which jobs need a compact part that stores a lot of energy over a long, controlled stroke, and which have alternatives such as weights, foam, rubber or electronics? The scenarios label those judgments as ideas.
Why springs are so useful
A spring is like an energy piggy bank.
Squash it and you put energy in. Let go and the energy comes back out as a push.
A spring is useful because it can store energy and give it back again and again. Squash it and you put energy in; let go and it pushes back with that energy.
Springs can also swing back and forth in a steady rhythm, like a ruler you twang on a desk. Clockmakers used that rhythm to keep time. And a spring can soak up a sudden bump and spread it out, which is why cars ride on them.
Springs do three distinct jobs. They store energy (½kx²) and release it on demand, as in a mainspring. They oscillate: a mass on a spring has a natural period, which a watch's balance spring uses as its regulator. And with a damper they isolate: a suspension spring deflects under a bump, while shock absorbers remove the energy so the car does not keep bouncing.
Removing springs removes all three functions at once, which is why the consequences differ so much between machines.
Springs in history
Long ago, heavy hanging weights made clocks go.
Then clockmakers used springs. Clocks got small enough to carry in a pocket!
The first mechanical clocks were driven by heavy hanging weights. Between 1500 and 1510, Peter Henlein of Nuremberg built clocks powered by springs instead, according to the U.S. National Institute of Standards and Technology. Without heavy weights, clocks could shrink into small, portable watches.
Around 1675, Christiaan Huygens added a tiny balance spring that swings back and forth. It helped pocket watches keep time to within about 10 minutes a day.
NIST's history of timekeeping credits Peter Henlein of Nuremberg with spring-powered clocks between 1500 and 1510; replacing drive weights allowed small, portable clocks and watches, although they ran slower as the mainspring unwound. Around 1675 Huygens developed the balance wheel and spring, letting 17th-century watches keep time to about 10 minutes a day.
By 1761 John Harrison's marine chronometer, with a spring and balance wheel escapement, kept time at sea to about a fifth of a second a day. Springs turned timekeeping from a fixed tower into something you could carry.
Amazing facts
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A plastic ruler is a little bit springy too.
Twang a plastic ruler on a desk and it wobbles back and forth. Its own springiness keeps pushing it back toward the middle.
OpenStax uses a plucked plastic ruler to show a restoring force: it oscillates about equilibrium until damping removes its energy.
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One click pen took a big team to design.
According to engineer Bill Hammack, the first Parker retractable pen, from 1954, took a team of 66 people to design.
Make magazine reports Bill Hammack's account that the 1954 Parker retractable pen took 66 people to design and has sold over three-quarters of a billion units.
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A sailing clock with springs kept very good time.
By 1761, John Harrison had built a sea clock with a spring and balance wheel that kept time on a rolling ship to about a fifth of a second a day.
NIST: Harrison's chronometer won the British longitude prize, keeping time at sea to about one-fifth of a second a day, ten times better than required.
Words to know
- spring
- a part that squashes or stretches and then returns to its shape
- Hooke's law
- the rule that a spring pushes back harder the farther it is squashed or stretched
- elastic
- able to return to its shape after being squashed or stretched
- potential energy
- stored energy, like the energy in a squashed spring
- shock absorber
- a part in a car that stops it from bouncing after a bump
Discovery challenge
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What does a spring do when you squash it and let go?
What does a squashed spring do when you let go?
When a compressed spring is released, its stored elastic energy…
- Springs back and pushes
- Stays squashed
- Disappears
Show the answer
Springs back and pushes
It springs back. Boing!
It springs back to its shape, pushing as it goes.
…becomes kinetic energy as it springs back.
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What made clocks small enough to carry?
What replaced heavy weights and let clocks become small enough to carry?
Which invention of 1500–1510 allowed portable clocks and watches?
- Springs
- Bigger weights
- Candles
Show the answer
Springs
Springs! Clocks no longer needed heavy weights.
Spring-powered clocks did away with heavy weights.
Spring-powered clocks, credited by NIST to Peter Henlein.
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What stops a car from bouncing after a bump?
Which car part stops the car bouncing up and down on its springs?
Which component damps a car's oscillation on its suspension springs?
- Shock absorbers
- Headlights
- The radio
Show the answer
Shock absorbers
Shock absorbers stop the bouncing.
Shock absorbers stop the bouncing.
Shock absorbers supply the damping.
Experiments to try
- Watch What If? Lab What if you played catch on a merry-go-round? Roll a ball straight across a spinning merry-go-round and, to the riders, it seems to curve away. Someone standing on the ground sees it go straight. The same trick, on our spinning Earth, bends winds and makes big storms swirl.
- Watch What If? Lab What if you could run at the speed of sound? Sound zips through air at about 343 meters per second, more than 30 times faster than the fastest human sprint. Anything that goes faster than sound pushes the air into a shock wave that people hear as a sonic boom. Imagine running that fast, then meet the jets that really do it.
Explore next
- Watch What If? Lab What if you played catch on a merry-go-round? Roll a ball straight across a spinning merry-go-round and, to the riders, it seems to curve away. Someone standing on the ground sees it go straight. The same trick, on our spinning Earth, bends winds and makes big storms swirl.
- Watch What If? Lab What if you could run at the speed of sound? Sound zips through air at about 343 meters per second, more than 30 times faster than the fastest human sprint. Anything that goes faster than sound pushes the air into a shock wave that people hear as a sonic boom. Imagine running that fast, then meet the jets that really do it.
- Watch Try it What If? Lab What if gravity disappeared? Gravity is the pull that makes a dropped ball fall and keeps your feet on the ground. Switch it off in our model and watch what a ball does instead, then find out why astronauts float.
- Watch Try it What If? Lab What if water were denser? Water pushes up on anything you put in it. A heavier, denser liquid pushes up harder. In our model, a block that sinks in water floats in a pretend liquid twice as dense, with only 60 percent of it under the surface.
- Watch Try it What If? Lab What if wheels were square? A square wheel on a flat road lifts its axle up and down with every corner. In our model it bounces almost 9 centimeters and loses most of its motion at each bump. On a road of curved humps, though, the same square rolls perfectly smoothly.
- Watch What If? Lab What if every surface were slippery? Friction is the grip between surfaces. It lets you walk, hold a pencil and stop a bike. Imagine a world where every surface was as slippery as ice, and follow what would happen to walking, writing and driving.
- Watch What If? Lab What if gravity pulled sideways? “Down” is simply the direction gravity pulls: toward the center of Earth. Imagine gravity pulling sideways instead, and follow what would happen to walking, to rivers, and to the very meaning of up and down.
- Watch What If? Lab What if you could see sound? Sound is a wave of squeezed and stretched air that our ears can feel but our eyes can't see. Imagine seeing it, then meet the real tools, like spectrograms and special cameras, that scientists use to turn sound and moving air into pictures.
For parents & teachers
What children will learn
- A spring pushes back harder the farther it is squashed or stretched (Hooke's law).
- Springs store energy and give it back.
- Springs made portable clocks and watches possible and help cars ride smoothly.
- A thought experiment separates measured facts from reasoned ideas.
Recommended ages: 7 to 17 · About 15 minutes
Talk about it
- How many springs can you find at home? Look in pens, staplers, doors and toys.
- Which jobs could something else do instead of a spring, and which could not?
- Why do you think springs helped clocks become small enough to carry?
Try at home or in class
- Take apart a click pen over a tray, find its spring and put it back together. What happens if you click it without the spring?
- Hold a plastic ruler flat on a table edge and twang the free end gently. Hold it shorter and try again. How does the wobble change?
Key vocabulary: spring, Hooke's law, elastic, potential energy, shock absorber
Where these facts come from
- College Physics 2e, §16.1 Hooke's Law: Stress and Strain Revisited , OpenStax
- A Walk Through Time: A Revolution in Timekeeping , National Institute of Standards and Technology
- A Walk Through Time: Early Clocks , National Institute of Standards and Technology
- How Does a Retractable Pen Work? , Make magazine
Checked, not yet human-reviewed. Last updated October 27, 2026. Spotted a mistake? Tell us.