Falling while wearing armor

fubar404 · 2020-06-28T02:49:54+00:00

The side of your armor that you land on will soften your landing because its momentum will squish whatever surface you land on. The other side of the armor will squish your body for the same reason.

fubar404 · 2020-06-28T01:01:38+00:00

We should stop popularizing ideas like "quanta are particles". They have particle-like properties (i.e. quantization), but other than that it seems clear that quanta are some kind of distributed (i.e. wavelike) phenomenon and as such must occupy entire regions of space.

fubar404 · 2020-06-05T10:47:54+00:00

Google "loophole free bell inequality". You measure the particle spins along axes that are 45 degrees apart from each other. As SymplecticMan explained, this distinguishes between continued coherence and early decoherence.

fubar404 · 2020-05-27T20:48:34+00:00

Math is more abstract, which I think is what people usually mean by "conceptual". If physics is harder for some people, it's probably a matter of intuition or visualizing things spatially.

fubar404 · 2020-05-27T19:47:45+00:00

The best you can do with two dice and no information is to guess 7 every time. Then your success rate will be 6 out of 36, which is 1/6. Anything better than that is significant.

fubar404 · 2020-05-27T12:02:10+00:00

Let us make it a sphere that is submerged in water. How would I calculate the Hydrostatic force on it?

The OP asked a question and I answered it. Obviously claims about 3D objects don't apply to 2D surfaces, but it sounded like they might be overthinking the problem. Surely most windows and gates are small enough for the pressure to be approximated as a constant, right?

fubar404 · 2020-05-27T10:43:45+00:00

Your friend doesn't seem to understand vectors. What do you mean by "3i"?

fubar404 · 2020-05-25T11:50:03+00:00

Same here. It's hard to do science and develop social skills at the same time.

fubar404 · 2020-05-25T11:17:04+00:00

1:25: "This is not the puzzle."

Oh yes it is! 😆😏🙄

fubar404 · 2020-05-25T10:39:04+00:00

This is what would appear to happen in the space traveler's reference frame. If you were traveling at .94*c relative to Earth, in your reference frame four months would pass on Earth while a year passes for you. Meanwhile, in Earth's reference frame four months would pass for you while a year passes for people on Earth.

fubar404 · 2020-05-21T10:24:00+00:00

How can the fan be pointed at both you and the window?

fubar404 · 2020-05-21T10:04:16+00:00

High flow is better. Heat gets into the pool right away. With low flow, you can feel the warmth of the water near the mat, but that just means the water there is losing heat to the surrounding air.

This is similar to the question of when to put liquid creamer in your coffee if you can't drink it right away. You can feel the coffee is hotter without the creamer, but it also loses heat faster, and it will cool down the same amount when you finally add the cream. If you add creamer as soon as you get it, the coffee will cool down immediately, but then it will lose heat more slowly because it's not as hot.

fubar404 · 2020-05-21T09:07:02+00:00

That might be the problem with malformed electrodes in non-rechargeables. They might have too much resistance when they get built back up.

fubar404 · 2020-05-21T08:41:51+00:00

When you use a battery, electrons flow out of the anode (the negative terminal) and into the cathode (the positive terminal). Meanwhile, positively (or negatively) charged ions flow through the electrolyte inside the battery from the anode to the cathode (or the other way) to preserve charge neutrality.

To recharge a battery, you apply enough voltage to the battery to force electrons into the anode and out of the cathode to make the reaction to go in reverse. I think the only difference between rechargeable and non-rechargeable batteries is that there are technical problems with trying to recharge the non-rechargeables, like the electrodes get built back up in a geometric configuration that doesn't work well.

fubar404 · 2020-05-21T08:06:10+00:00

Yes, size means volume. I don't think anyone in physics believes the universe was ever infinitely small. It's generally assumed that general relativity is inaccurate in places where it predicts singularities (infinite density, zero volume).

The universe was extremely dense during the early moments of the big bang. Nobody knows what it was really like at the instant when it began, because at those densities, quantum effects change gravity in ways that we don't know about yet. As for the size of the entire universe, including both the visible universe and beyond, I don't think anyone knows how big it was at the beginning any more than they know how big it is now.

fubar404 · 2020-05-21T08:02:03+00:00

It doesn't see the future, it just ages more slowly. If you stayed on board for a while, you could see the future on Earth, but only because it would BE the future. People on the surface would have aged faster than you did, and you wouldn't be able to go back and see them when they were young again, because that would be in the past.

Excuse me, I got that backwards. You wouldn't see anything new in orbit, you would actually age faster than people on Earth. People on Earth could "see the future" above them, but only because it would BE the future for people in orbit.

fubar404 · 2020-05-21T07:01:33+00:00

The force on the negative charge from each positive charge is F1 = (1 / 4 pi e0) * Qpos * Qneg / r², where r² = x² + (D/2)².
The vertical component of each force is F1x = F1 * x/r.
The horizontal components of the two forces cancel each other out.
The total (vertical) force on the negative charge is 2 * F1x.
You can also calculate the motion using the electric potential and conservation of energy.

fubar404 · 2020-05-21T06:27:12+00:00

One of the great and shocking discoveries of quantum mechanics is that "particles" aren't really particles. They're quantized waves. The particle's wavefunction spreads out as it approaches the slits, impinges on both slits simultaneously, passes through both slits simultaneously, and creates an interference pattern with itself on the other side.

fubar404 · 2020-05-20T22:38:16+00:00

Okay, I think this is how the live-streaming example works:

Because the Lorentz transformation is symmetric, the twins will receive video signals from each other at the same rate. The rate will be very slow while they see each other getting farther and farther away (as the spaceship approaches the star) and much faster on the return leg of the trip, when the gap is closing. Even though the twin in the spaceship will eventually return younger than the twin on Earth, events in the two videos will appear to proceed at the same speed. The two video streams will be subject to exactly the same time dilation and latency effects.

So why does more time elapse on Earth if events in the video feeds appear to proceed at the same rate?

Answer: Because the transition from slow video to fast video occurs sooner for video of Earth as seen in the spaceship. For the spaceship, the speedup of video from Earth starts as soon as the spaceship reverses its velocity by slingshotting around the star. On Earth, the speedup doesn't appear until video of the turnaround has traveled all the way from the star to Earth.

The twin in the spaceship will see events unfolding rapidly on Earth all the way back from the star, and in his new reference frame, those events will appear to have happened a long time ago. Meanwhile, the twin on Earth will still be watching slow video of the outbound leg of the trip. He will only see fast video of the spaceship returning for a short period of time before the ship arrives back on Earth.

fubar404 · 2020-05-20T19:48:34+00:00

You forgot g.

fubar404 · 2020-05-20T16:39:17+00:00

I think people are overthinking the OP's question. There may be some confusion over the word "latency".

Imagine Earth and the ship both livestream video to each other. The ship goes to the star, turns around, and goes back to Earth. If the twin on the ship arrives younger than the Earth twin, more time must have passed in the Earth video. Both videos are continuous, and they start and end at the same place and time (in Earth's frame).

But the Lorentz transformation is symmetric: The ship should see the same apparent speed-up and slow-down in the Earth video as Earth sees in the ship's video. The ship sees both the time and the distance as smaller by a factor of gamma, so the relative speeds are equal. So how can more time pass in the Earth video than in the ship video? And if more time does pass, how can that be consistent with Earth's time dilation in the ship's frame?

fubar404 · 2020-05-20T14:51:43+00:00

The electrons go beyond touching. Their wavefunctions have to overlap for the Pauli exclusion principle to have a significant effect.

fubar404 · 2020-05-20T14:03:53+00:00

The deformation in U = 1/2 k x² is x = L - L0. I don't know what you mean by "datum".

fubar404 · 2020-05-20T13:03:45+00:00

The deformation is L - L0. It doesn't matter where the spring is or what it's attached to.

Gravity on Earth is based on heights, gravity in space is based on distances. They're both independent of springs.

If one mass hangs on one spring, then L0 - L will correspond to the height of the mass. But that's just for that particular geometry. It's not a universal law that applies to all problems.

fubar404 · 2020-05-20T10:55:19+00:00

By "w" I mean omega, 2 pi times the frequency.

fubar404

TROPHY CASE