Bare Hand Bottle Busting- Science Investigation

Kevin and I get to the bottom of a science mystery using only our wits and rugged good looks.

MUSIC-

Summary:
Using the Scientific Method and with the help of the Backyard Scientist, we determine how someone can break a glass bottle with their bare hands.

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I make videos like this once a month all year long while supplies last:

[TheKingofRandom]

Rubber mallet is a good idea. I can't tell you how many times I hurt my hand trying this.

[roz]

You two guys are definitely Phineas and Ferb

[jacoblee]

Literally every time:
Mark Rober: High-Speed Projectiles!
Backyard Scientist: Set Everything on Fire!

[TheRussellStover]

This never gets old watching it again.

[eliwoolums]

When they both had different theories I was like oh no it’s like the two smart kids in class getting different answers

[benjaminmeyers]

I totally think that Mark Rober, Backyard Scientist and the Slow-Mo guys need to make some of these videos together

[zerdeaths]

Tried it at home.
Broke all the beer bottles in my fridge.
Now dad is beating me.
Thank you. *very* much...

[isCarsonMiller]

Me after watching this video: “excuse me, friend, can I interest you in this delicious bottle of hot water?”

[antsinmyeyes]

Imagine pulling out some kerosene snowballs during a snowball fight

[asheryellen]

Me: It's definitely just air pressure
mark: It's not air pressure


Me: It's not air pressure

[James-tvbm]

5:22

Who the hell screams ”gonnorhea” when they hurt themselves

[c]

From a fluid dynamics perspective:
It seems to me that hitting the top of the bottle sends a shockwave through the water. Shockwaves have extremely low pressure at the front of the shock and extremely high pressure at the back of the shock. When the front of the wave reaches the bottom of the bottle, that low pressure zone generated by the shockwave induces cavitation (the little pocket of vapor you see at the bottom of the bottle). The water cant hold onto the air bubbles that are already dissolved in it or stay in its liquid phase in this low pressure zone, similar to why boiling water is much easier at the top of a mountain; the atmospheric pressure is less. When the energy of the shockwave dissipates, this vapor bubble (cavitation) collapses...very, very, violently. Often times at supersonic speeds. The force of that vapor bubble collapsing at supersonic speeds (which brings the water crashing down onto the bottom of the bottle), is what breaks the bottle, in my opinion. Perhaps Schlieren imaging could confirm this.

It would follow that the CO2 bubbles in carbonation interrupt this shock wave from passing through the liquid, and keep the wave from reaching the bottom with enough energy to induce cavitation. The low pressure zone generated by the shockwave would cause the CO2 bubbles to escape from the liquid, causing the foaming in the beer you see

This phenomenon is very similar to the cavitation seen in boat propellers. The propeller spins through the water, generating a low pressure zone behind the blades of the propeller, and when this pressure is low enough, the water can no longer stay in it's liquid phase, releasing any dissolved gas and changing phase to water vapor, generating the vapor bubble you see behind the propeller. When the energy from the propeller dissipates, these vapor bubbles collapse at supersonic speeds, changing the phase back to liquid and dissolving any air/gases back into the water, but at the same time gouging a chunk of metal out of the propeller.

Edit: I've edited this post to clarify a few things, thanks to those who commented below!

[slashinini]

*The Slow-Mo Guys wants to know your location*

[abhiramjoshi]

5:12 "this is glass"
jerryrig : "glass is glass and glass can break"

[jamesstorie]

Funny how he uses a corona bottle for the water

[surajmishra]

"So as firm believers of science..." when you hear that

[creyoxxx]

"You should set those on fire"
Yes throwing fire balls at kids will be fun

[bb]

I learned to do this forty plus years ago, while in college. I always did this the hard way, with coke bottles having thicker glass. Plus seeing why this works would have led to better results.

[razzi]

3:55 Says they put red colour in The bottle to see The break easier.. shows clip of a bottle with a clear liquid

[juice]

*SET IT ON FIRE*
-Kevin (The Backyard Scientist) 2016