Help me geeks, you're my only hope (physics "riddle" inside)

So a colleague linked me to this browser game, where you have to build a catapult out of pencils and whatnot to launch an eraser across an office.

I have no intention of competing for the grand price, but it bugs the hell out of me, that I’m second last in our little league with my piddling 317 cm (the best in the league is 444 cm and the overall best is 839 cm).

Post your solutions and help me get above 400 cm… that’s all I ask. Then perhaps I will be able to get some work done again.

The best solution will receive my recipe for the cake pictured to the left of my pitiful latest attempt.

Went over 400 several times, first replace the lever with the longest pencil, and drop the eraser from max height, this allows it to impart a bit more energy. After that it was just experimenting with positioning to get the best launch, and roll is important. Oh, and jack up the entire lever assembly with the sharpeners and maybe another pen, the trick is to let the apple be able to move the pencil through a nearly-full range.


Drop the eraser from max height?

454 with initial lever and only modifiyng the location of the fulcrum and the projectile.

I noticed that the slightest variation in positioning can have a huge impact on the outcome.
This encourages too much fiddling around and is kind of lame.

replace orange pencil with the red one, it’s bigger so you get more force

I got around 420 before I remembered that A) I had no way to share my configuration and B) 90 minutes had passed and I hadn’t done anything but this goddam game.

There’s a computer monitor you can briefly see in the background that shows off a pretty complicated setup. I have no idea how you manually turn things, though. I don’t read European. So I couldn’t give it a try.

use the arrow keys with an item selected.

You can turn things? God dammit!

I hate this game.

continues playing

Well, setting up this:

Gave me this:

I found that even minute changes in the eraser’s rotation and drop position could affect the total distance by 100cm or so. The key to this iteration was that it ending up spinning rapidly when it hit the ground, and gained > 100cm rolling and jumping.

WTF … you an move the start orange too?

I hate this game.

still continues playing

Well, dropping the eraser may or may not be a valid mechanism, because it seems like getting a good eraser landing/spin is a more important component.

I changed the launch point/eraser rotation to this:

And it had such a fast, jumpy landing spin that I ended up with this:

If getting a good eraser bounce/roll going is the only way to get up to those distances then that throws actual physics right out the window and makes it about empirically trying to find the best starting condition based on the unknown equations that the game is using to calculate bouncing and all that.

EDIT: My best was like 350, but my eraser was stopping dead/bouncing backwards every time it hit the ground.

Just some observations on this:

  1. The fulcrum has to have enough density and friction not to slide around when the orange hits the lever. The pen cap works well because sometimes it seems to “flex”, which could possibly be imparting additional force to the lever. The grey sharpener is worth experimenting with, as well, as it is has both high density and friction; otoh, its fulcrum point is wider than the pen cap, which lessens its effectiveness.

  2. The fulcrum point has to be high enough off the desk that the orange and its lever side can swing down to a ~90 degree angle. You also can’t have things in the way to impede that swing.

Argh! I held the record at 447 for a few minutes this morning, but that just made the others mad… now I have to beat 511 and I can’t get baluts results with that design.
No actual work will be done.

Argh! No one told me this!

I wonder what kind of effect this game has on Danish GDP.

Just got this result (I noticed Hanzii is at #17):

By using this design:

Some design notes:

  1. I think a key component is reducing the energy lost to the catapult system by the orange drop. To reduce energy lost by the sliding base/fulcrum, I added additional high-friction, high-mass weights behind the pencil lead “base”.

1a. BUT, I found that limiting the pivot movement of the cracker fulcrum itself by putting blocks behind it reduced the catapult power; to this end, I made sure that enough room existed to allow the cracker fulcrum to pivot upon the orange impact.

  1. The orange itself bleeds energy by shifting to the right upon impact with the red pencil; to reduce this, I placed the cake as a buffer to make sure that the majority of the orange movement is downward. The hard part is making sure that the cake doesn’t reduce the impact of the orange or absorb too much of its energy.

2a. I might have to experiment with using a leaning pencil/pen as an orange drop shunt, instead of the cake.

  1. The eraser angle definitely makes a difference, as different ground impacts and rolls occur.

  2. Oddly enough, the placement of the leftmost pen cap/lever support affects the catapult launch power, even if moved by a few pixels.

You can rotate stuff? Dagnabbit, if I had done that, I might have beaten Balut’s score :( Now I’m in between Hanzii and Balut.

…with this variant, which uses a cake/pen/pencil buttress to prevent the orange from sliding to the right after impact, and also lengthens the orange impact side of the lever by a cm or so:

I can typically get between 350-380cm upon launch, and then getting the right eraser roll/bounce accounts for the rest of the distance.