# physics demonstration

So last month my Physics teacher demonstrated sound waves using fire and Bohemian Rhapsody. The song is played into a tube filled with gas, and the sound waves cause the gas to compress, changing the height of the flames (I think that was how he explained it anyways)

Pascal’s Law tells us that pressure in a fluid depends on the height and density of the fluid. This is something that you’ve experienced firsthand if you’ve ever tried to dive in deep water. The deeper into the water you swim, the greater the pressure you feel, especially in your ears. Go deep enough and the pressure difference between your inner ear and the water becomes outright painful.

In the video demonstration above, you’ll see how a tall, thin tube containing only 1 liter of water is able to shatter a 50-liter container of water. Not only does this show just how powerful height is in creating pressure in a fluid, but it shows how a fluid can be used to transmit pressure over a distance – one of the fundamental principles of hydraulics! (Video credit: K. Visnjic et al.; submitted by Frederik B.)

If a random pop song taken completely out of context is not an accurate soundtrack for a physics demonstration, you can safely ignore that demonstration as you will learn nothing useful.
—  Physics professor
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This is an Euler’s Disk. It’s a physics toy that demonstrates angular momentum, potential energy, and kinetic energy.

## Behold, Physics!

In this stunning demonstration, the Myth-busters fired a soccer ball at 50 mph out of a cannon on a truck riding at 50 mph in the opposite direction.

The ball just falls down as if it is free falling!! This is a consequence of the fact that in Newtonian mechanics, opposite vector quantities cancel out each other. You probably have heard that a legion times, but here’s the visual proof.

Sometimes I feel that textbooks butcher elegant concepts by excluding visuals during the explanation. But again, if one could incorporate gifs onto books the world would definitely be a better place. :)

This video demonstrates one of my favorite effects: the reversibility of laminar flow. Intuition tells us that un-mixing two fluids is impossible, and, under most circumstances, that is true. But for very low Reynolds numbers, viscosity dominates the flow, and fluid particles will move due to only two effects: molecular diffusion and momentum diffusion. Molecular diffusion is an entirely random process, but it is also very slow. Momentum diffusion is the motion caused by the spinning inner cylinder dragging fluid with it. That motion, unlike most fluid motion, is exactly reversible, meaning that spinning the cylinder in reverse returns the dye to its original location (plus or minus the fuzziness caused by molecular diffusion).

Aside from being a neat demo, this illustrates one of the challenges faced by microscopic swimmers. In order to move through a viscous fluid, they must swim asymmetrically because exactly reversing their stroke will only move the fluid around them back to is original position. (Video credit: Univ. of New Mexico Physic and Astronomy)

Yes, that’s right, I am a wizard.
—  Physics professor after doing the bicycle wheel gyroscope demonstration
erin gilbert notes
• i think it’s too often glossed over that erin gilbert, canonically, is considered “an asset to modern physics.”
• she got her undergraduate education at the university of michigan - ann arbor which has the #1 ranked nuclear engineering, #11 ranked physics and #11 ranked particle physics departments in the country. she then spent a brief time at MIT which is the #1 physics department in the country before finishing up her graduate and post-graduate education at princeton, the #2 physics department in the country.
• she’s up for tenure at columbia university, tied with michigan as the 11th best physics department in the U.S. getting to the point where any teacher is up for tenure isn’t easy. and being up for tenure at such a prestigious university? erin has worked more than hard, and there’s no understating that not only has she worked hard but her contributions have been recognized as valuable enough to be a tenure candidate.
• in the movie, erin has at least 5 framed awards from the american physical society on her office wall. the only name i was able to catch is the apker award. the leroy apker award is given, yearly, to two (only two!) young physicists who exemplify high achievement in undergraduate physics and have demonstrated “great potential for future scientific accomplishment.” the other awards are likely to be just as prestigious.
• so let’s just all really appreciate that high-strung, awkward, sometimes emotionally maladjusted erin gilbert went into a STEM field dominated by men, thrived in the soul-gutting world of professional academia and essentially made it her bitch before peacing out to pursue her real, fulfilling passion, and she almost immediately contributes to legitimizing a fringe science. she’s ambitious. she’s dedicated. she’s goal-oriented. and she’s friggin’ brilliant.
• don’t. sleep. on. erin. gilbert.

lol u guys i have this really hot physics demonstrator at uni

if this post gets 500 notes ill write “me please” on my prac where it asks for the date AHAHAH

A boiled and peeled egg is sucked through a bottle neck that it is too big to fit through

HOW?

The air in the atmosphere exerts atmospheric pressure. When the paper was lit, the air inside the bottle got hotter and expanded. Some of the air escaped from the bottle. When the flame went out, the air inside the bottle cooled down and contracted- the air pressure decreased considerably.

This meant that the atmospheric pressure outside the bottle was greater than that of inside the bottle. This pushed the egg into the bottle.

This is the same practical mentioned earlier on this blog, except this time me and a colleague tried to film it ourselves. The force pulling the egg into the conical flask was so strong, that it broke the egg apart (something tells me that egg isn’t coming out whole….)

gif Source: The CoolScienceGifs lab

Supercooling is the process of lowering a fluid’s temperature below its freezing point without the fluid becoming solid. Though this may sound bizarre, it’s an effect you can recreate easily in your refrigerator, as detailed in the video above. Supercooling shows up in nature as well, particularly with water droplets at high altitudes. If a plane flies through supercooled water droplets, it can create icing problems on the aircraft’s wings. Alternatively, flying through supercooled water vapor can cause a hole-punch cloud to form when the vapor flash-freezes into snow. (Video credit: SciShow)

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Physics educator James Lincoln helps people understand the natural world. The gifs above are from a Youtube video he made on how to “see” an electric field, the region around a charged object where electric force is experienced. When the object is positively charged, electric field lines extend radially outward from the object. When the object is negatively charged, the lines extend radially inward.

Click the gifs for more info or see the full video below.

MHA dub commentary episode 7:

(this one got so long i had to put it under a readmore)

• it’s been a while since i last saw an episode so i’m gonna have to readjust to hearing everyone’s dub voices again
• i think it’s kinda interesting how Bakugou actually ask’s someone else’s opinion on Izuku having a quirk here, since usually he wouldn’t ask anyone else on their opinion on anything
• especially since it’s Iida and on the first day they were already not getting along
• “Was he seriously just tricking me all these years?” and heeeere is the start of all of Bakugou’s personal problems, oh boy
• i always enjoyed how Izuku still admires Bakugou despite all of his bad qualities. he’s not gonna let Bakugou win this tho, no matter what, he’s just gotta try harder this time
• the scene with the splitscreen when All Might announces the start of the battle looks weirdly drawn to me
• aaannnd here comes Bakugou. he has absolutely no chill whatsoever
• oh we’re still on the recap lmao
• kinda odd but Uraraka’s little squeak as she was pushed out of the way of Bakugou’s attack was adorable
• i was gonna say “I wonder where Izuku got those fighting moves from” but then i realized it was from hauling all that trash
• and now he’s….. hauling…. Bakugou……..
• …………………. there’s a “taking out the trash” joke in there somewhere
• i’m sorry Bakugou (…. tho you were pretty awful early on so)
• baby Izuku’s voice is so fucking cute

Imagine you are a new meta-human and you meet the Flash

“So, you are this red streak I have heard so much about.” You say as you circle around the man in the red suit. “Look, I don’t want to hurt you, so leave me alone!”

“I’m here to help you.” He takes a step towards you and before you realize it, he is right in front of you.

“Why? We don’t even know each other.”

“I go by the Flash, and I am a meta-human, like you. I have the ability to run really fast.” You stare at him for a moment, not sure if you should trust him, but you look in his eyes and something inside of you relaxes.

“I can defy the laws of physics.” You demonstrate your powers by lifting up a car with your hand and putting it back down. “I can do much more than that, but I am also very dangerous, I can’t control it sometimes.”

“Come with me to Star Labs, we can help.” The Flash holds out his hand, and you take it. He smiles at you and you can’t help but smile back.

F=MA:B. Force = Mass x Acceleration x Brotherhood
—  Roommate demonstrating excellent physics knowledge

# Why Physicists Love Super Balls

by Joel N. Shurkin, Inside Science

Super Balls are toys beloved by children because of their extraordinary ability to bounce. Physicists love them for exactly the same reason.

Drop a baseball on the floor and it will hardly bounce at all. Drop a Super Ball from shoulder height, and it will bounce back 92 percent of the way to the drop-off point. Super Balls also are just as bouncy vertically as they are horizontally, and they spin oddly.

“Physicists love it because it has interesting physical properties,” said Rod Cross, retired professor of physics at the University of Sydney in Australia, whose latest paper on Super Balls appears in the American Journal of Physics. His research also demonstrated the odd way all balls roll.