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phetsims / collision-lab

"Collision Lab" is an educational simulation in HTML5, by PhET Interactive Simulations.
GNU General Public License v3.0
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Tunneling ball in 1D collisions #122

Closed arouinfar closed 3 years ago

arouinfar commented 4 years ago

A user wrote into phethelp:

I think there might be a bug in the Collisions simulation.

Under the Advanved tab, if you choose one-dimension and have three balls with different masses, say 0.1 kg, 1 kg, and 5 kg, you can see balls "tunneling" through each other so that if they start out 1, 3, 2 you might get 3, 1, 2 and then it will switch back to 1, 3, 2 or might change to 3, 2, 1 (where the numbering is the ordering of the balls L-R inside the rectangle). It happens mostly when the balls are moving fast, although they never are traveling fast enough to approach speeds for QM tunneling.

I bring it up because it raises a question on whether or not this bug might be affecting the simulation in other areas. If I assign it as an online "lab" activity for a physics course, but the data is corrupt, it makes it difficult for students to deal with the simulation data.

I was able to reproduce this bug in Flash if the initial velocities are high. It's also possible to do in the HTML5 version.

Initial state: image

At some point ball 1 tunnels through ball 2: image

brandonLi8 commented 4 years ago

This was addressed in #123, which has now been merged into master. Back to @arouinfar for review.

arouinfar commented 4 years ago

Master is looking really good!! I haven't been able to reproduce the tunneling, but I think it would be good for QA to check on this when it goes up for testing.

KatieWoe commented 3 years ago

Haven't reproduced in dev.10

brooklynlash commented 3 years ago

I noticed something similar on Windows 10 Chrome, but unsure if tunneling or just that the objects can overlap. Only works if you add balls in when the pink ball is at an area past where the new balls go in, and it looks like once they separate they don't go through each other again. capacitortunnel2

KatieWoe commented 3 years ago

Great catch!. It might be a separate issue though. @arouinfar what is your verdict?

arouinfar commented 3 years ago

Nice find @brooklynlash. I think @KatieWoe is correct. This looks like a slightly different issue, so I've opened #179.

KatieWoe commented 3 years ago

Still seems fixed. Found something related to #179 but since it is a separate issue now, I think this can be closed. For 1.1.0 dev.13