The Physics of Roller Coasters

Imagine being strapped into a big chunk
of metal raised over a hundred twenty meters into the sky and then dropped
whizzing over hills and even looping upside down. When you put it that way roller coasters can seem a little
terrifying but they’re also exhilarating and involve some really interesting
physics make all those speedy gut dropping thrills work. Most roller
coasters start off with something called a lift hill, which mechanically lifts you to
the top of the first and tallest hill. But other roller coasters start a little
more suddenly. They’re rapidly propelled forward thanks the hydraulics – the branch
of physics that deals with fluids and how different mechanical forces affect
them. Hydraulic launch systems work by using a cable that’s attached to two
important pieces: a catch-car which connects to the bottom of
the roller coaster train and a giant winch which is basically a huge spool
that winds the cable when it’s turned by some motor. So, to launch the train this
cable pulls it down the tracks like reeling in a fish really fast. After a
few seconds the Catch-car releases the train so it can zoom up the big hill. It’s
kind of a complex mechanism but we’ll go over the basics. The hydraulic fluid and some
nitrogen gas are separated by a piston inside this chamber called the hydraulic
accumulator. And the key to these launch systems is the fact that liquids, like
hydraulic fluid, are incompressible. So the hydraulic fluid is pumped into the
accumulator and compresses the nitrogen gas so there’s more gas molecules
bouncing around in a smaller space, which increases the pressure. Nitrogen gas is
cheap, easy to get, and won’t react dangerously to heat and high pressure.
Basically no huge explosions. And once the pressure is high enough, a valve is
opened and the hydraulic fluid rushes out to power a bunch of motors, which
turn the winch, which pulls the cable and accelerates the train. Just like that,
within a couple seconds you’re speeding along at hundreds of kilometers per hour.
So now that the ride started you’ve made it to the top of the first hill and you
start to head over the other side you might feel something weird. Like besides
the adrenaline or other chemicals that give you that exciting rush. There’s that
sinking feeling in your stomach and you might feel weightless. That’s because
you’re in freefall – meaning that gravity is the only force acting on your body.
Normally throughout the day you’re able to feel your weight because something
like the ground or a chair is pushing back on your body from your feet to your
bones and organs. But when you’re in freefall you’re not being supported by
anything, so there isn’t a force pushing upward on you. You’re just accelerating toward
the earth at 9.8 meters per second squared like any other falling object.
Now all good or slightly terrifying things have to come to an end so the
roller coaster train needs to stop somehow. Traditionally roller coasters
use breaks that coming contact with a speeding train like
something that skids along the bottom or clamps that close round metal fins on
the cars. These breaks rely on friction which causes the kinetic energy, the
energy of motion, to be converted into heat energy and stops the train. And
these brakes work but they get worn out from all this contact. But there are some
breaks that don’t involve friction. They work by moving a conductor like the
metal pins sticking out from the train through a magnetic field. A magnetic
field can be produced by electric currents, like the currents running
through a wire or the microscopic currents formed by electrons moving
within atoms, which is kinda helped permanent magnets work. So on the tracks
of some roller coasters there are rows of permanent magnets that create a
magnetic field. And when the metal fins pass through the magnetic field it
induces a ring-like current called an eddy current. This has to do with Lenz’s
law which essentially tells us that conductors like these metal fins don’t
like change. So when the fins enter a magnetic field that wasn’t there before,
they’ll create a current that makes its own magnetic field that opposes this
change. The train will slow down because the kinetic energy of the moving train
is dissipated as heat by the eddy currents flowing through the metal. And
eventually the train comes to a stop all without friction. So whether you love ’em
or hate ’em, hopefully knowing some of the physics behind roller coasters can
make you appreciate them a little more. Thank you for watching this episode of
SciShow, brought to you by our patrons on patreon. If you wanna help support the
show you can go to patreon.com/scishow and don’t forget to go to youtube.com/scishow and subscribe. If I move my hand closer to this antenna the pitch will go up and over here
closer and farther within this one I can control the volume it’s like magic but it’s……

Stephen Childs


  1. 0:25 is kingda ka in six flags of new jersey, it launches you incredibly fast and you're already back from the ride in like 20 seconds

  2. Could you please also do an episode about the heart line and the shape of loopings. Thx

  3. Are you wearing that shirt comically, as in getting a glass of water, not falling asleep on the beach without an alarm set, etc?
    Or, are you wearing it to warn people about the importance of having a final will notarized and assigning someone the power of attorney before taking a long dirt nap?

  4. DUDE! Make one about the physics of Motorcycles! You will find there's a lot of fascinating nerdy stuff about them!

  5. And then there are roller coasters that want to kill you, like Magnum XL-200 and Skyrush. The airtime is intense on those.

  6. I feel that this episode could be 20-30 minutes. There is a lot more to this. 🙂

  7. My physics teacher's version of "You have to walk before you can run" was "You have to learn to resolve forces before you can build rollercoasters."

  8. I would love to see how the enteric nervous system and the brain communicate back and forth when doing things like riding a roller coaster.

  9. I'm no physicist but I'm pretty sure you don't accelerate at 9.8 m/s² unless you're falling straight down, which on a roller coaster, you're falling at an angle, so you'd accelerate slightly slower.

  10. Hey SciShow – Linear Induction Motors…. Look it up, quite neat… cough chough, railguns, cough, disneyland, cough, california screamin, cough…

  11. Eddy current brakes cannot bring a roller coaster to a complete stop. As the velocity decreases, the strength of the eddy currents also decreases, causing a decreased braking force. Friction brakes are required to fully stop the train and hold it in place.

  12. Liquids are compressible. However, the effects are negligible at those pressures.

  13. Wait, you showed Kingda Ka for hydraulic launch system, but I though Kingda Ka was magnetic

  14. ok, I call bullsh*t, no roller-coaster propels occupants at "hundreds of miles per hour".
    one would expect a science based web program to at the very least report reasonably accurate information.

  15. You didn't mention magnetic launchers / linear induction motors like the Mr. Freeze in Six Flags Over Texas at Arlington.

  16. While you were at it, you should've also talked about the heartline and how banking turns work and the physics of G-force. Any NoLimits users here?

  17. no offence my nigga but I hate the accents on scishow. I like the content but the accents just fucking piss me off. This video is ok but that other fucking guy with his accent shits me off.

  18. A little note, these magnetic brakes also generate heat when the eddy current dissipate… Law of conservation of energy again

  19. can u make a video of why we use speacial type of shoes on ice skating? why dont we use normal shoes they would be more safe?

  20. Was at King's Dominion the other day. Pretty sure I got a concussion from all the rides that felt the need to stop within like 2 seconds. "Gradually come to a stop" my ass; for some reason they feel the need to slam on the breaks to stop the car even when they've got a bunch of track left -_-

  21. i was at Disneyland in LA some years ago and a couple of the roller coasters used electromagnetic launchers to go up the hills rather than the usual mechanical launchers

  22. no mention of the adding/subtracting weights & changing wheel materials to get the coaster to go all the way around & not get stuck.

    Or even the power setting vs weight of people & wheel material (friction) to launch a coaster.


    no mention of not just making it all the way around, but going fast enough that you're pinned in your seat and don't fall or float in your seat when upside down (very freaky feeling that happens on Canada's wonderland's 'the bat' if your restraint isn't 100% tight/you puff out your chest when they close it)


    Going so fast you get G-loc




    Get a neck or spinal injury from changing axis direction to quickly


    i could go on, but THAT is the science of rollar coasters

  23. Why is actually called a hydraulic launch system instead of a pneumatic or (semi-hydraulic or semi-pneumatic), because the liquids are merely used to charge the system, the nitrogen gas seems to be doing the actual pushing of the liquid through the motors, according to the schematic shown. Or is it because "fluid dynamics" deal with both liquids and gases?

  24. Is there a single roller coaster in the world that uses eddy current as breaks ? Please provide a link to article or case study. Many thanks, Luke.

  25. could've done with some impressive stats on the forces involved in average roller coasters. maybe a mention of fastest speeds, highest G-forces, largest loops, etc. and some shout outs to the engineers and designers, who have to work the physics into real-life constructions. safety mechanisms could also use a good mention, along with what happens when they're ignored or fail.

    i should become a scriptwriter for SciShow.

  26. +SciShow : A slight mistake: A permanent magnet can't stop a train, because its strenght is related to the velocity. The higher the velocity is, the stronger the braking force will be, which is quite handy. But on the other hand, the lower the speed is, the weaker the braking is… So in the end it can't stop the train, in theory. In reality, friction (both air and contact friction) will do the job, but manufacturer usually have a friction brake or a friction tire at the end for that purpose.

  27. how about making an uphill part towards the end of track so gravity slows the roller coaster/

  28. I thought I've understood something until that eddy current shit. After I forgot whatever I understood

  29. You forgot about lagoons wicked. It uses electro magnetics to shoot it up over its hill. It is a really fun experience because there is No hesitation when going up the huge hill, you simply hear some sirens, turn a small corner, and then you get to the magnets and shoot up.

  30. If I go on a loop on a roller coaster, would I stay in my seat (like when you swing a cup of water around in a circle and the water stays in the cup.), or would my shoulders rest against the restraint?

  31. That is basically how the Tower Bridge in opened.( except they use water instead of nitrogen gas)

  32. There are more type of rollercoaster launches than just hydraulic launches such as pneumatic etc

  33. What about linear synchronous motors and linear induction motors!!!??? (LSM, LIM)

  34. I am so proud of you for not saying that you don't fall out of a vertical loop in a roller coaster because of the forces. That explanation for loops fails to explain why you don't fall out of any other element.

  35. sinking feeling in your stomach? guys feel that in their balls, just saying.

  36. I thought you were about to explain how it advances, how the wheels interact with the rail. I meani it's not like the usual train wheel right? Or is it?

  37. I was on the Red Force rollercoaster and I asked myself- How is this even possible? Being 112m above the ground accelerating to 180[km/h] within only 5 seconds, with the massive overload on the railway track. I really liked The Paraborollercoaster… (a.k.a Red Force).

  38. Millenium Force Thumbnail. I Rode it. Its fun, and very well explained, but that picture of Millenium Force after the launch explanation, but Millenium Force isn't a launch coaster.

  39. the fact i learned about is when the rollercoaster is going fast that creates gas and energy while the rollercoaster is in motion.

  40. Actually, the magnetic brakes aren't enough to bring the train to a complete stop, so they do include some friction brakes after the magnetic brakes.

  41. Excellent video. This guy's a top dog. Expert physics explanations without dumbing it down for John and Jane Q America

  42. So roller coaster are not machine operated after the hill drop? Its pure velocity that keeps it running?

  43. The picture of the skid brakes is a picture on the Thunderbolt in Kennywood in West Mifflin, PA. My home amusement park. So cool

  44. this really was just about kingda ka or top thrill dragster which is what? two or three roller coasters that do this? I wanna know the physics of why they can seemingly loop and loop forever even after it seems like it slowed down too much to do another loop

  45. i was disapointed at the video all i did was look direcly at his shirt/side note sorry about the grammer

  46. Man this video glossed over so much. You just cannot do this topic justice in 3 minutes. It felt so rushed with no real detail

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