this post was submitted on 29 Apr 2026
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xkcd #3239: Simple Machines

Title text:

It's hard to decide which simple machine system to invest in. DeWalt makes a great lever and inclined plane, but I hear Milwaukee's wheel-and-axles are really good.

Transcript:

Transcript will show once it’s been added to explainxkcd.com

Source: https://xkcd.com/3239/

explainxkcd for #3239

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[–] NoSpotOfGround@lemmy.world 69 points 2 weeks ago* (last edited 2 weeks ago) (4 children)
[–] GorGor@startrek.website 33 points 2 weeks ago (3 children)

I seem to remember wedge was basically an inclined plane, and a screw was an inclined plane wrapped around an axle. Also a pulley is a specific application of wheel and axle.

[–] wonderingwanderer@sopuli.xyz 3 points 2 weeks ago

And incline planes and axles are both types of levers 🤯

[–] Redjard@reddthat.com 1 points 2 weeks ago

The difference between wedge and inclined plane is that the wedge uses friction to create a ratchet. You hit wedges but push stuff on an inclined plane.
The screw is similar, it can be screwed continuously or ratcheted, and it will rest in its final position under the same friction. Though you can also see stuff like locktight lock it in place when the friction is insufficient, so in theory you could have a screw that self unscrews without that.

The pulley transfers the force/energy through it from the ropes end, For the axle, one end is combined with the axle and rotates with it. This I would say is a special case of the pulley, but also is quite bad. You need to slap a rotating lever on the end as a big handle to actually gain anything.

The pulley nor the spool give you mechanical advantage. For pulley systems the advantage comes from combining the redirection properties of pulleys, and for spools they come from the handle acting as a lever.
The spool doesn't really redirect thogh, you could tie the rope directly to the handle and get the same advantage. The spool is just to collect the rope so you can keep turning without reattaching the lever. It extends your stroke.

[–] DarkCloud@lemmy.world 1 points 2 weeks ago (1 children)

But is a lever an adjustable inclined plane, or is it a specific application of a wheel and axel?

[–] UnimportantHuman@lemmy.ml 9 points 2 weeks ago (1 children)

Is it all inclined planes????

[–] LogicalDrivel@sopuli.xyz 6 points 2 weeks ago

🌍 🧑‍🚀 🔫 🧑‍🚀

[–] TheTechnician27@lemmy.world 16 points 2 weeks ago

Arrange all six in series for some great slapstick.

[–] panda_abyss@lemmy.ca 13 points 2 weeks ago (2 children)

Aren’t scrwws just a fancy inclined plane?

[–] arctanthrope@lemmy.world 8 points 2 weeks ago

and aren't inclined planes just a fancy wedge

[–] Derpenheim@lemmy.zip 3 points 2 weeks ago (2 children)

Screws convert rotational energy into directional energy

[–] panda_abyss@lemmy.ca 4 points 2 weeks ago (1 children)

TIL the definition of simple machine.

[–] Alcoholicorn@mander.xyz 7 points 2 weeks ago (1 children)
[–] Swedneck@discuss.tchncs.de 6 points 2 weeks ago

"behold a screw!"

[–] Riverside@reddthat.com 1 points 2 weeks ago (1 children)

Movement rather than energy

[–] Derpenheim@lemmy.zip 1 points 2 weeks ago

Fair its all kinetic energy

[–] Agent641@lemmy.world 12 points 2 weeks ago

I used a wedge and hammer last night to split one very large limestone block into 5 more manageable ones and I've never felt more ancient Egyptian in my life.

[–] DarrinBrunner@lemmy.world 9 points 2 weeks ago (1 children)
[–] ShaggyBlarney@lemmy.ca 7 points 2 weeks ago

Like all things in life, [insert action] is just a degenerate form of bending. -Bender Bending Rodríguez

[–] NeatNit@discuss.tchncs.de 4 points 2 weeks ago

I can see the screw, pulley, and wedge (the tip). In a pinch, the whole thing can act as a lever. But I can't see any wheel and axle (no, the pulley isn't one), and there's definitely no inclined plane. Randall got ripped off.

[–] itsjustachairmary@lemmy.world 2 points 2 weeks ago

Ok but can a cow use it?

[–] Cocodapuf@lemmy.world 1 points 2 weeks ago

It's hard to decide which simple machine system to invest in. DeWalt makes a great lever and inclined plane, but I hear Milwaukee's wheel-and-axles are really good.

I think Randall really gets my life.

[–] Uranus_Hz@lemmy.zip 1 points 2 weeks ago